Client-Server API Go

This project consists of two Go programs (client.go and server.go) that demonstrate how to consume an external API, save data in a SQLite database, and manipulate files using standard Go packages and external packages.

Description

• client/client.go: A client that makes an HTTP request to the server (server/server.go) to request the USD to BRL exchange rate and saves the received value in a text file.
• server/server.go: A server that consumes an external API to obtain the USD to BRL exchange rate, returns the result to the client in JSON format, and logs the exchange rate in a SQLite database.

Requirements

• Go 1.18 or higher
• SQLite3

Setup

1. Initialize Go Modules:

   go mod init github.com/pansani/client-server-api

2. Install Dependencies:

   go get github.com/mattn/go-sqlite3

3. Structure: Ensure your project structure looks like this:

   client-server-api-go/
   ├── client/
   │   └── client.go
   ├── server/
   │   └── server.go
   ├── cotacao.txt
   ├── cotacoes.db
   ├── go.mod
   └── go.sum
   

Running the Project

Running the Server

1. Open a terminal and navigate to the server directory.
2. Run the server:

   go run server.go

3. The server will start and listen on port 8080.

Running the Client

1. Open another terminal and navigate to the client directory.
2. Run the client:

   go run client.go

3. The client will make a request to the server, receive the exchange rate, and save it in the cotacao.txt file.

Functionality

• Server:

  • Fetches the USD to BRL exchange rate from the API https://economia.awesomeapi.com.br/json/last/USD-BRL with a timeout of 200ms.
  • Saves the fetched exchange rate in a SQLite database with a timeout of 10ms.
  • Provides an endpoint /cotacao that returns the current exchange rate in JSON format.

• Client:

  • Makes a request to the server's /cotacao endpoint with a timeout of 300ms.
  • Saves the received exchange rate in a file named cotacao.txt in the format: Dólar: {value}.

Error Handling

• The server logs errors if the request to the external API or the database operation exceeds the timeout.
• The client logs errors if the request to the server exceeds the timeout or if there is an error saving to the file.

Example Output

• cotacao.txt:

  Dólar: 5.42