diff --git a/Makefile b/Makefile
index 427c26e..eb8f74a 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,3 @@
-.PHONY:easyjson
-easyjson:
-	easyjson -all ./internal/model/config.go
-
 .PHONY:build
 build:
 	go build .
diff --git a/go.mod b/go.mod
index 1bd9ed4..4e148ea 100644
--- a/go.mod
+++ b/go.mod
@@ -3,7 +3,6 @@ module github.com/sanposhiho/gomockhandler
 go 1.16
 
 require (
-	github.com/mailru/easyjson v0.7.7
 	golang.org/x/mod v0.4.1
 	golang.org/x/sync v0.0.0-20190423024810-112230192c58
 )
diff --git a/go.sum b/go.sum
index 8e073dc..de71f05 100644
--- a/go.sum
+++ b/go.sum
@@ -1,7 +1,3 @@
-github.com/josharian/intern v1.0.0 h1:vlS4z54oSdjm0bgjRigI+G1HpF+tI+9rE5LLzOg8HmY=
-github.com/josharian/intern v1.0.0/go.mod h1:5DoeVV0s6jJacbCEi61lwdGj/aVlrQvzHFFd8Hwg//Y=
-github.com/mailru/easyjson v0.7.7 h1:UGYAvKxe3sBsEDzO8ZeWOSlIQfWFlxbzLZe7hwFURr0=
-github.com/mailru/easyjson v0.7.7/go.mod h1:xzfreul335JAWq5oZzymOObrkdz5UnU4kGfJJLY9Nlc=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/crypto v0.0.0-20191011191535-87dc89f01550/go.mod h1:yigFU9vqHzYiE8UmvKecakEJjdnWj3jj499lnFckfCI=
 golang.org/x/mod v0.4.1 h1:Kvvh58BN8Y9/lBi7hTekvtMpm07eUZ0ck5pRHpsMWrY=
diff --git a/internal/command/generate_config.go b/internal/command/generate_config.go
index 393c079..362b89e 100644
--- a/internal/command/generate_config.go
+++ b/internal/command/generate_config.go
@@ -44,7 +44,7 @@ func (r Runner) GenerateConfig() {
 	destinationPathInPro := util.PathInProject(configDir, originalPath+"/"+r.Args.Destination)
 	r.MockgenRunner.SetDestination(destinationPathInPro)
 
-	var sourceChecksum [16]byte
+	var sourceChecksum string
 	if r.Args.Source != "" {
 		// change source as seen from the config directory.
 		sourcePathInPro := util.PathInProject(configDir, originalPath+"/"+r.Args.Source)
diff --git a/internal/command/mockgen.go b/internal/command/mockgen.go
index ae6a755..ab2b532 100644
--- a/internal/command/mockgen.go
+++ b/internal/command/mockgen.go
@@ -35,7 +35,7 @@ func (r Runner) Mockgen() {
 		m := m
 		g.Go(func() error {
 			var runner mockgen.Runner
-			var sourceChecksum [16]byte
+			var sourceChecksum string
 			switch m.Mode {
 			case model.ReflectMode:
 				runner = m.ReflectModeRunner
diff --git a/internal/mockgen/runner.go b/internal/mockgen/runner.go
index 39fa414..936e49c 100644
--- a/internal/mockgen/runner.go
+++ b/internal/mockgen/runner.go
@@ -16,7 +16,7 @@ type Runner interface {
 	GetDestination() string
 }
 
-func Checksum(r Runner) ([16]byte, error) {
+func Checksum(r Runner) (string, error) {
 	d := r.GetDestination()
 	tmpFile := util.TmpFilePath(d)
 	defer os.Remove(tmpFile)
@@ -26,21 +26,21 @@ func Checksum(r Runner) ([16]byte, error) {
 	defer r.SetDestination(d)
 
 	if err := r.Run(); err != nil {
-		return [16]byte{}, fmt.Errorf("failed to run mockgen: %v \nPlease run `%s` and check if mockgen works correctly with your options", err, r)
+		return "", fmt.Errorf("failed to run mockgen: %v \nPlease run `%s` and check if mockgen works correctly with your options", err, r)
 	}
 
 	checksum, err := util.CalculateCheckSum(tmpFile)
 	if err != nil {
-		return [16]byte{}, fmt.Errorf("calculate checksum of the mock: %v", err)
+		return "", fmt.Errorf("calculate checksum of the mock: %v", err)
 	}
 
 	return checksum, nil
 }
 
-func SourceChecksum(r Runner) ([16]byte, error) {
+func SourceChecksum(r Runner) (string, error) {
 	checksum, err := util.CalculateCheckSum(r.GetSource())
 	if err != nil {
-		return [16]byte{}, fmt.Errorf("calculate checksum of the mock source: %v", err)
+		return "", fmt.Errorf("calculate checksum of the mock source: %v", err)
 	}
 
 	return checksum, nil
diff --git a/internal/model/config.go b/internal/model/config.go
index 6c76588..d8ffd70 100644
--- a/internal/model/config.go
+++ b/internal/model/config.go
@@ -2,7 +2,6 @@ package model
 
 import "errors"
 
-//easyjson:json
 type Config struct {
 	// key: destination
 	Mocks map[string]*Mock `json:"mocks"`
diff --git a/internal/model/config_easyjson.go b/internal/model/config_easyjson.go
deleted file mode 100644
index 2f1946d..0000000
--- a/internal/model/config_easyjson.go
+++ /dev/null
@@ -1,636 +0,0 @@
-// Code generated by easyjson for marshaling/unmarshaling. DO NOT EDIT.
-
-package model
-
-import (
-	json "encoding/json"
-	easyjson "github.com/mailru/easyjson"
-	jlexer "github.com/mailru/easyjson/jlexer"
-	jwriter "github.com/mailru/easyjson/jwriter"
-	reflectmode "github.com/sanposhiho/gomockhandler/internal/mockgen/reflectmode"
-	sourcemode "github.com/sanposhiho/gomockhandler/internal/mockgen/sourcemode"
-)
-
-// suppress unused package warning
-var (
-	_ *json.RawMessage
-	_ *jlexer.Lexer
-	_ *jwriter.Writer
-	_ easyjson.Marshaler
-)
-
-func easyjson6615c02eDecodeGithubComSanposhihoGomockhandlerInternalModel(in *jlexer.Lexer, out *Config) {
-	isTopLevel := in.IsStart()
-	if in.IsNull() {
-		if isTopLevel {
-			in.Consumed()
-		}
-		in.Skip()
-		return
-	}
-	in.Delim('{')
-	for !in.IsDelim('}') {
-		key := in.UnsafeFieldName(false)
-		in.WantColon()
-		if in.IsNull() {
-			in.Skip()
-			in.WantComma()
-			continue
-		}
-		switch key {
-		case "mocks":
-			if in.IsNull() {
-				in.Skip()
-			} else {
-				in.Delim('{')
-				out.Mocks = make(map[string]*Mock)
-				for !in.IsDelim('}') {
-					key := string(in.String())
-					in.WantColon()
-					var v1 *Mock
-					if in.IsNull() {
-						in.Skip()
-						v1 = nil
-					} else {
-						if v1 == nil {
-							v1 = new(Mock)
-						}
-						easyjson6615c02eDecodeGithubComSanposhihoGomockhandlerInternalModel1(in, v1)
-					}
-					(out.Mocks)[key] = v1
-					in.WantComma()
-				}
-				in.Delim('}')
-			}
-		default:
-			in.SkipRecursive()
-		}
-		in.WantComma()
-	}
-	in.Delim('}')
-	if isTopLevel {
-		in.Consumed()
-	}
-}
-func easyjson6615c02eEncodeGithubComSanposhihoGomockhandlerInternalModel(out *jwriter.Writer, in Config) {
-	out.RawByte('{')
-	first := true
-	_ = first
-	{
-		const prefix string = ",\"mocks\":"
-		out.RawString(prefix[1:])
-		if in.Mocks == nil && (out.Flags&jwriter.NilMapAsEmpty) == 0 {
-			out.RawString(`null`)
-		} else {
-			out.RawByte('{')
-			v2First := true
-			for v2Name, v2Value := range in.Mocks {
-				if v2First {
-					v2First = false
-				} else {
-					out.RawByte(',')
-				}
-				out.String(string(v2Name))
-				out.RawByte(':')
-				if v2Value == nil {
-					out.RawString("null")
-				} else {
-					easyjson6615c02eEncodeGithubComSanposhihoGomockhandlerInternalModel1(out, *v2Value)
-				}
-			}
-			out.RawByte('}')
-		}
-	}
-	out.RawByte('}')
-}
-
-// MarshalJSON supports json.Marshaler interface
-func (v Config) MarshalJSON() ([]byte, error) {
-	w := jwriter.Writer{}
-	easyjson6615c02eEncodeGithubComSanposhihoGomockhandlerInternalModel(&w, v)
-	return w.Buffer.BuildBytes(), w.Error
-}
-
-// MarshalEasyJSON supports easyjson.Marshaler interface
-func (v Config) MarshalEasyJSON(w *jwriter.Writer) {
-	easyjson6615c02eEncodeGithubComSanposhihoGomockhandlerInternalModel(w, v)
-}
-
-// UnmarshalJSON supports json.Unmarshaler interface
-func (v *Config) UnmarshalJSON(data []byte) error {
-	r := jlexer.Lexer{Data: data}
-	easyjson6615c02eDecodeGithubComSanposhihoGomockhandlerInternalModel(&r, v)
-	return r.Error()
-}
-
-// UnmarshalEasyJSON supports easyjson.Unmarshaler interface
-func (v *Config) UnmarshalEasyJSON(l *jlexer.Lexer) {
-	easyjson6615c02eDecodeGithubComSanposhihoGomockhandlerInternalModel(l, v)
-}
-func easyjson6615c02eDecodeGithubComSanposhihoGomockhandlerInternalModel1(in *jlexer.Lexer, out *Mock) {
-	isTopLevel := in.IsStart()
-	if in.IsNull() {
-		if isTopLevel {
-			in.Consumed()
-		}
-		in.Skip()
-		return
-	}
-	in.Delim('{')
-	for !in.IsDelim('}') {
-		key := in.UnsafeFieldName(false)
-		in.WantColon()
-		if in.IsNull() {
-			in.Skip()
-			in.WantComma()
-			continue
-		}
-		switch key {
-		case "checksum":
-			if in.IsNull() {
-				in.Skip()
-			} else {
-				copy(out.MockCheckSum[:], in.Bytes())
-			}
-		case "source_checksum":
-			if in.IsNull() {
-				in.Skip()
-			} else {
-				copy(out.SourceChecksum[:], in.Bytes())
-			}
-		case "mode":
-			out.Mode = mode(in.String())
-		case "reflect_mode_runner":
-			if in.IsNull() {
-				in.Skip()
-				out.ReflectModeRunner = nil
-			} else {
-				if out.ReflectModeRunner == nil {
-					out.ReflectModeRunner = new(reflectmode.Runner)
-				}
-				easyjson6615c02eDecodeGithubComSanposhihoGomockhandlerInternalMockgenReflectmode(in, out.ReflectModeRunner)
-			}
-		case "source_mode_runner":
-			if in.IsNull() {
-				in.Skip()
-				out.SourceModeRunner = nil
-			} else {
-				if out.SourceModeRunner == nil {
-					out.SourceModeRunner = new(sourcemode.Runner)
-				}
-				easyjson6615c02eDecodeGithubComSanposhihoGomockhandlerInternalMockgenSourcemode(in, out.SourceModeRunner)
-			}
-		default:
-			in.SkipRecursive()
-		}
-		in.WantComma()
-	}
-	in.Delim('}')
-	if isTopLevel {
-		in.Consumed()
-	}
-}
-func easyjson6615c02eEncodeGithubComSanposhihoGomockhandlerInternalModel1(out *jwriter.Writer, in Mock) {
-	out.RawByte('{')
-	first := true
-	_ = first
-	if true {
-		const prefix string = ",\"checksum\":"
-		first = false
-		out.RawString(prefix[1:])
-		out.Base64Bytes(in.MockCheckSum[:])
-	}
-	if true {
-		const prefix string = ",\"source_checksum\":"
-		if first {
-			first = false
-			out.RawString(prefix[1:])
-		} else {
-			out.RawString(prefix)
-		}
-		out.Base64Bytes(in.SourceChecksum[:])
-	}
-	{
-		const prefix string = ",\"mode\":"
-		if first {
-			first = false
-			out.RawString(prefix[1:])
-		} else {
-			out.RawString(prefix)
-		}
-		out.String(string(in.Mode))
-	}
-	if in.ReflectModeRunner != nil {
-		const prefix string = ",\"reflect_mode_runner\":"
-		out.RawString(prefix)
-		easyjson6615c02eEncodeGithubComSanposhihoGomockhandlerInternalMockgenReflectmode(out, *in.ReflectModeRunner)
-	}
-	if in.SourceModeRunner != nil {
-		const prefix string = ",\"source_mode_runner\":"
-		out.RawString(prefix)
-		easyjson6615c02eEncodeGithubComSanposhihoGomockhandlerInternalMockgenSourcemode(out, *in.SourceModeRunner)
-	}
-	out.RawByte('}')
-}
-func easyjson6615c02eDecodeGithubComSanposhihoGomockhandlerInternalMockgenSourcemode(in *jlexer.Lexer, out *sourcemode.Runner) {
-	isTopLevel := in.IsStart()
-	if in.IsNull() {
-		if isTopLevel {
-			in.Consumed()
-		}
-		in.Skip()
-		return
-	}
-	in.Delim('{')
-	for !in.IsDelim('}') {
-		key := in.UnsafeFieldName(false)
-		in.WantColon()
-		if in.IsNull() {
-			in.Skip()
-			in.WantComma()
-			continue
-		}
-		switch key {
-		case "source":
-			out.Source = string(in.String())
-		case "destination":
-			out.Destination = string(in.String())
-		case "package":
-			out.Package = string(in.String())
-		case "imports":
-			out.Imports = string(in.String())
-		case "aux_files":
-			out.AuxFiles = string(in.String())
-		case "mock_names":
-			out.MockNames = string(in.String())
-		case "self_package":
-			out.SelfPackage = string(in.String())
-		case "copyright_file":
-			out.CopyrightFile = string(in.String())
-		case "write_pkg_comment":
-			if in.IsNull() {
-				in.Skip()
-				out.WritePkgComment = nil
-			} else {
-				if out.WritePkgComment == nil {
-					out.WritePkgComment = new(bool)
-				}
-				*out.WritePkgComment = bool(in.Bool())
-			}
-		case "debug_parser":
-			if in.IsNull() {
-				in.Skip()
-				out.DebugParser = nil
-			} else {
-				if out.DebugParser == nil {
-					out.DebugParser = new(bool)
-				}
-				*out.DebugParser = bool(in.Bool())
-			}
-		default:
-			in.SkipRecursive()
-		}
-		in.WantComma()
-	}
-	in.Delim('}')
-	if isTopLevel {
-		in.Consumed()
-	}
-}
-func easyjson6615c02eEncodeGithubComSanposhihoGomockhandlerInternalMockgenSourcemode(out *jwriter.Writer, in sourcemode.Runner) {
-	out.RawByte('{')
-	first := true
-	_ = first
-	if in.Source != "" {
-		const prefix string = ",\"source\":"
-		first = false
-		out.RawString(prefix[1:])
-		out.String(string(in.Source))
-	}
-	if in.Destination != "" {
-		const prefix string = ",\"destination\":"
-		if first {
-			first = false
-			out.RawString(prefix[1:])
-		} else {
-			out.RawString(prefix)
-		}
-		out.String(string(in.Destination))
-	}
-	if in.Package != "" {
-		const prefix string = ",\"package\":"
-		if first {
-			first = false
-			out.RawString(prefix[1:])
-		} else {
-			out.RawString(prefix)
-		}
-		out.String(string(in.Package))
-	}
-	if in.Imports != "" {
-		const prefix string = ",\"imports\":"
-		if first {
-			first = false
-			out.RawString(prefix[1:])
-		} else {
-			out.RawString(prefix)
-		}
-		out.String(string(in.Imports))
-	}
-	if in.AuxFiles != "" {
-		const prefix string = ",\"aux_files\":"
-		if first {
-			first = false
-			out.RawString(prefix[1:])
-		} else {
-			out.RawString(prefix)
-		}
-		out.String(string(in.AuxFiles))
-	}
-	if in.MockNames != "" {
-		const prefix string = ",\"mock_names\":"
-		if first {
-			first = false
-			out.RawString(prefix[1:])
-		} else {
-			out.RawString(prefix)
-		}
-		out.String(string(in.MockNames))
-	}
-	if in.SelfPackage != "" {
-		const prefix string = ",\"self_package\":"
-		if first {
-			first = false
-			out.RawString(prefix[1:])
-		} else {
-			out.RawString(prefix)
-		}
-		out.String(string(in.SelfPackage))
-	}
-	if in.CopyrightFile != "" {
-		const prefix string = ",\"copyright_file\":"
-		if first {
-			first = false
-			out.RawString(prefix[1:])
-		} else {
-			out.RawString(prefix)
-		}
-		out.String(string(in.CopyrightFile))
-	}
-	if in.WritePkgComment != nil {
-		const prefix string = ",\"write_pkg_comment\":"
-		if first {
-			first = false
-			out.RawString(prefix[1:])
-		} else {
-			out.RawString(prefix)
-		}
-		out.Bool(bool(*in.WritePkgComment))
-	}
-	if in.DebugParser != nil {
-		const prefix string = ",\"debug_parser\":"
-		if first {
-			first = false
-			out.RawString(prefix[1:])
-		} else {
-			out.RawString(prefix)
-		}
-		out.Bool(bool(*in.DebugParser))
-	}
-	out.RawByte('}')
-}
-func easyjson6615c02eDecodeGithubComSanposhihoGomockhandlerInternalMockgenReflectmode(in *jlexer.Lexer, out *reflectmode.Runner) {
-	isTopLevel := in.IsStart()
-	if in.IsNull() {
-		if isTopLevel {
-			in.Consumed()
-		}
-		in.Skip()
-		return
-	}
-	in.Delim('{')
-	for !in.IsDelim('}') {
-		key := in.UnsafeFieldName(false)
-		in.WantColon()
-		if in.IsNull() {
-			in.Skip()
-			in.WantComma()
-			continue
-		}
-		switch key {
-		case "package_name":
-			out.PackageName = string(in.String())
-		case "interfaces":
-			out.Interfaces = string(in.String())
-		case "source":
-			out.Source = string(in.String())
-		case "destination":
-			out.Destination = string(in.String())
-		case "package":
-			out.Package = string(in.String())
-		case "imports":
-			out.Imports = string(in.String())
-		case "aux_files":
-			out.AuxFiles = string(in.String())
-		case "build_flags":
-			out.BuildFlags = string(in.String())
-		case "mock_names":
-			out.MockNames = string(in.String())
-		case "self_package":
-			out.SelfPackage = string(in.String())
-		case "copyright_file":
-			out.CopyrightFile = string(in.String())
-		case "exec_only":
-			out.ExecOnly = string(in.String())
-		case "prog_only":
-			if in.IsNull() {
-				in.Skip()
-				out.ProgOnly = nil
-			} else {
-				if out.ProgOnly == nil {
-					out.ProgOnly = new(bool)
-				}
-				*out.ProgOnly = bool(in.Bool())
-			}
-		case "write_pkg_comment":
-			if in.IsNull() {
-				in.Skip()
-				out.WritePkgComment = nil
-			} else {
-				if out.WritePkgComment == nil {
-					out.WritePkgComment = new(bool)
-				}
-				*out.WritePkgComment = bool(in.Bool())
-			}
-		case "debug_parser":
-			if in.IsNull() {
-				in.Skip()
-				out.DebugParser = nil
-			} else {
-				if out.DebugParser == nil {
-					out.DebugParser = new(bool)
-				}
-				*out.DebugParser = bool(in.Bool())
-			}
-		default:
-			in.SkipRecursive()
-		}
-		in.WantComma()
-	}
-	in.Delim('}')
-	if isTopLevel {
-		in.Consumed()
-	}
-}
-func easyjson6615c02eEncodeGithubComSanposhihoGomockhandlerInternalMockgenReflectmode(out *jwriter.Writer, in reflectmode.Runner) {
-	out.RawByte('{')
-	first := true
-	_ = first
-	if in.PackageName != "" {
-		const prefix string = ",\"package_name\":"
-		first = false
-		out.RawString(prefix[1:])
-		out.String(string(in.PackageName))
-	}
-	if in.Interfaces != "" {
-		const prefix string = ",\"interfaces\":"
-		if first {
-			first = false
-			out.RawString(prefix[1:])
-		} else {
-			out.RawString(prefix)
-		}
-		out.String(string(in.Interfaces))
-	}
-	if in.Source != "" {
-		const prefix string = ",\"source\":"
-		if first {
-			first = false
-			out.RawString(prefix[1:])
-		} else {
-			out.RawString(prefix)
-		}
-		out.String(string(in.Source))
-	}
-	if in.Destination != "" {
-		const prefix string = ",\"destination\":"
-		if first {
-			first = false
-			out.RawString(prefix[1:])
-		} else {
-			out.RawString(prefix)
-		}
-		out.String(string(in.Destination))
-	}
-	if in.Package != "" {
-		const prefix string = ",\"package\":"
-		if first {
-			first = false
-			out.RawString(prefix[1:])
-		} else {
-			out.RawString(prefix)
-		}
-		out.String(string(in.Package))
-	}
-	if in.Imports != "" {
-		const prefix string = ",\"imports\":"
-		if first {
-			first = false
-			out.RawString(prefix[1:])
-		} else {
-			out.RawString(prefix)
-		}
-		out.String(string(in.Imports))
-	}
-	if in.AuxFiles != "" {
-		const prefix string = ",\"aux_files\":"
-		if first {
-			first = false
-			out.RawString(prefix[1:])
-		} else {
-			out.RawString(prefix)
-		}
-		out.String(string(in.AuxFiles))
-	}
-	if in.BuildFlags != "" {
-		const prefix string = ",\"build_flags\":"
-		if first {
-			first = false
-			out.RawString(prefix[1:])
-		} else {
-			out.RawString(prefix)
-		}
-		out.String(string(in.BuildFlags))
-	}
-	if in.MockNames != "" {
-		const prefix string = ",\"mock_names\":"
-		if first {
-			first = false
-			out.RawString(prefix[1:])
-		} else {
-			out.RawString(prefix)
-		}
-		out.String(string(in.MockNames))
-	}
-	if in.SelfPackage != "" {
-		const prefix string = ",\"self_package\":"
-		if first {
-			first = false
-			out.RawString(prefix[1:])
-		} else {
-			out.RawString(prefix)
-		}
-		out.String(string(in.SelfPackage))
-	}
-	if in.CopyrightFile != "" {
-		const prefix string = ",\"copyright_file\":"
-		if first {
-			first = false
-			out.RawString(prefix[1:])
-		} else {
-			out.RawString(prefix)
-		}
-		out.String(string(in.CopyrightFile))
-	}
-	if in.ExecOnly != "" {
-		const prefix string = ",\"exec_only\":"
-		if first {
-			first = false
-			out.RawString(prefix[1:])
-		} else {
-			out.RawString(prefix)
-		}
-		out.String(string(in.ExecOnly))
-	}
-	if in.ProgOnly != nil {
-		const prefix string = ",\"prog_only\":"
-		if first {
-			first = false
-			out.RawString(prefix[1:])
-		} else {
-			out.RawString(prefix)
-		}
-		out.Bool(bool(*in.ProgOnly))
-	}
-	if in.WritePkgComment != nil {
-		const prefix string = ",\"write_pkg_comment\":"
-		if first {
-			first = false
-			out.RawString(prefix[1:])
-		} else {
-			out.RawString(prefix)
-		}
-		out.Bool(bool(*in.WritePkgComment))
-	}
-	if in.DebugParser != nil {
-		const prefix string = ",\"debug_parser\":"
-		if first {
-			first = false
-			out.RawString(prefix[1:])
-		} else {
-			out.RawString(prefix)
-		}
-		out.Bool(bool(*in.DebugParser))
-	}
-	out.RawByte('}')
-}
diff --git a/internal/model/mock.go b/internal/model/mock.go
index 4c0a19b..7b16190 100644
--- a/internal/model/mock.go
+++ b/internal/model/mock.go
@@ -15,14 +15,14 @@ const (
 )
 
 type Mock struct {
-	MockCheckSum      [16]byte            `json:"checksum,omitempty"`
-	SourceChecksum    [16]byte            `json:"source_checksum,omitempty"`
+	MockCheckSum      string              `json:"checksum,omitempty"`
+	SourceChecksum    string              `json:"source_checksum,omitempty"`
 	Mode              mode                `json:"mode"`
 	ReflectModeRunner *reflectmode.Runner `json:"reflect_mode_runner,omitempty"`
 	SourceModeRunner  *sourcemode.Runner  `json:"source_mode_runner,omitempty"`
 }
 
-func NewMock(mockChecksum, sourceChecksum [16]byte, genrunner mockgen.Runner) Mock {
+func NewMock(mockChecksum, sourceChecksum string, genrunner mockgen.Runner) Mock {
 	rrunner, srunner := convertMockgenRunner(genrunner)
 	mode := Unknown
 	if rrunner != nil {
diff --git a/internal/repository/config/config.go b/internal/repository/config/config.go
index f8d1aea..e1b5c01 100644
--- a/internal/repository/config/config.go
+++ b/internal/repository/config/config.go
@@ -7,7 +7,6 @@ import (
 	"io/ioutil"
 	"os"
 
-	"github.com/mailru/easyjson"
 	"github.com/sanposhiho/gomockhandler/internal/model"
 )
 
@@ -18,9 +17,9 @@ func NewRepository() Repository {
 }
 
 func (r *Repository) Put(m *model.Config, path string) error {
-	d, err := easyjson.Marshal(m)
+	d, err := json.Marshal(m)
 	if err != nil {
-		return fmt.Errorf("easyjson marshal: %w", err)
+		return fmt.Errorf("json marshal: %w", err)
 	}
 
 	var buf bytes.Buffer
@@ -42,9 +41,9 @@ func (r *Repository) Get(path string) (*model.Config, error) {
 	}
 
 	var m model.Config
-	err = easyjson.Unmarshal(raw, &m)
+	err = json.Unmarshal(raw, &m)
 	if err != nil {
-		return nil, fmt.Errorf("easyjson unmarshal: %w", err)
+		return nil, fmt.Errorf("json unmarshal: %w", err)
 	}
 
 	return &m, err
diff --git a/internal/util/random.go b/internal/util/random.go
index 5ea02d4..5b23013 100644
--- a/internal/util/random.go
+++ b/internal/util/random.go
@@ -2,20 +2,22 @@ package util
 
 import (
 	"crypto/md5"
+	"encoding/base64"
 	"fmt"
 	"io/ioutil"
 	"path/filepath"
 	"strings"
 )
 
-func CalculateCheckSum(filePath string) ([16]byte, error) {
+func CalculateCheckSum(filePath string) (string, error) {
 	file, err := ioutil.ReadFile(filePath)
 	if err != nil {
-		return [16]byte{}, fmt.Errorf("failed read file. filename: %s, err: %w", filePath)
+		return "", fmt.Errorf("failed read file. filename: %s, err: %w", filePath)
 	}
 
 	hash := md5.Sum(file)
-	return hash, nil
+	strhash := base64.StdEncoding.EncodeToString(hash[:])
+	return strhash, nil
 }
 
 func PathInProject(projectRoot, path string) string {