GET<\/code>, POST<\/code>, PUT<\/code>, DELETE<\/code>, etc.) and handle requests and responses in a structured manner. The Gorilla Mux package is easy to use, and the package supports a range of middleware that you can use for logging and authentication operations, among others.<\/p>\n<\/a>Getting Started Building Applications in Go<\/h2>\nGetting started with building REST APIs with Go is quite easy. First, you must install the latest Go version on your system. The installation process is straightforward. Simply visit the Go downloads webpage to install the Go binary distribution for your computer\u2019s operating system.<\/p>\n
Run this command on your terminal to verify that you\u2019ve successfully installed Go.<\/p>\n
go version<\/pre>\nOnce you have installed Go, the next step is creating a new directory and initializing the directory as a Go project.<\/p>\n
Run these commands on your terminal to create and initialize a new Go project on your computer.<\/p>\n
mkdir HumanAPI && cd HumanAPI\r\ngo mod init HumanAPI<\/pre>\nThe go mod<\/code> command initializes a new Go project in the specified working directory. The command also creates a go.mod file in the directory for managing your project\u2019s dependencies.<\/p>\nFinally, you\u2019ll need some form of persistence for your database. In this tutorial, you\u2019ll learn how to use GORM and a SQL database for persistence for your API. GORM supports a variety of SQL databases, including MSSQL, MySQL, and PostgreSQL. Install your preferred database management system, and you\u2019re good to go.<\/a><\/p>\nBuilding APIs with Gorilla Mux<\/h2>\n
The Gorilla Mux<\/a> package is a third-party package, and you\u2019ll need to install the package as one of your project\u2019s dependencies to get started.<\/p>\nRun this command in the terminal of your project\u2019s working directory to install the Gorilla Mux package.<\/p>\n
go get github.com\/gorilla\/mux<\/pre>\nHere\u2019s how to import the Gorilla Mux package into your Go files.<\/p>\n
import \"github.com\/gorilla\/mux\"<\/pre>\nYou\u2019ll need to create a new router instance to work with handler functions with the Gorilla Mux package. You can use the NewRouter<\/code> function to create a new router instance.<\/p>\nrouter := mux.NewRouter()<\/pre>\nAfter creating a router instance, you can use the HandleFunc<\/code> function to map handler functions to routes and specify the HTTP method for the routes.<\/p>\nfunc main() {\r\n\trouter := mux.NewRouter()\r\n \trouter.HandleFunc(\"\/humans\/{id}\", \r\n getHuman).Methods(\"GET\")\r\n\trouter.HandleFunc(\"\/humans\", createHuman).Methods(\"POST\")\r\n\trouter.HandleFunc(\"\/humans\/{id}\", \r\n updateHuman).Methods(\"PUT\")\r\n\trouter.HandleFunc(\"\/humans\/{id}\", \r\n deleteHuman).Methods(\"DELETE\")\r\n\tlog.Fatal(http.ListenAndServe(\":8080\", router))\r\n}<\/pre>\nThe main<\/strong> function above creates a new router instance and mounts routes to GET<\/code>, POST<\/code>, PUT<\/code>, and DELETE<\/code> requests before starting a server on port :8080<\/code> with the ListenAndServe<\/code> function of the http<\/code> package.<\/p>\n<\/a>Setting Persistence Up GORM for the API<\/h2>\nMost of the time, you\u2019ll need persistence when building APIs for data storage and retrieval. GORM<\/a> is the most popular ORM in the Go ecosystem, and the package is useful for working with many databases.<\/p>\nRun this command to install the GORM package and the SQLite database driver for the package.<\/p>\n
go get gorm.io\/gorm\r\ngo get gorm.io\/driver\/sqlite \/\/SQLite<\/pre>\nYou can learn more about GORM from this article if you\u2019re unfamiliar with the package. The article covers the most popular operations with the package while considering other databases.<\/p>\n
Here\u2019s the list of imports you\u2019ll need to set up the API, including Gorilla Mux, GORM, and Go built-in packages.<\/p>\n
import(\r\n \"encoding\/json\"\r\n \"fmt\"\r\n \"log\"\r\n \"net\/http\"\r\n \"github.com\/gorilla\/mux\"\r\n \"gorm.io\/driver\/sqlite\"\r\n \"gorm.io\/gorm\"\r\n)<\/pre>\nYou\u2019ll need a struct model that defines the database schema for queries and data migration. Here\u2019s an example struct for the database schema.<\/p>\n
type Human struct {\r\n\tID uint `gorm:\"primaryKey\"`\r\n\tAge int `json:\"age\"`\r\n\tName string `json:\"name\"`\r\n}<\/pre>\nThe ID<\/code> field is the primary key, and the Age<\/code> and Name<\/code> fields are regular fields.<\/p>\nYou\u2019ll need to access your database instance from multiple handler functions, so you can resort to making it a global variable for accessibility. The DB<\/code> struct defines a GORM database instance.<\/p>\nvar (\r\n\tdb *gorm.DB\r\n\terr error\r\n)<\/pre>\nYou can use a function to manage database auto migrations. You\u2019ll use the Open<\/code> function of the gorm<\/code> package to open a database connection from the driver. The sqlite<\/code> package\u2019s Open<\/code> function returns a connection instance that GORM can access and return a database instance.<\/p>\nAfter creating a database instance, you can use the AutoMigrate<\/code> function of the database instance that takes in the struct model and auto-migrates struct instances.<\/p>\nfunc DBConnection() error {\r\n\tdb, err = gorm.Open(sqlite.Open(\"test.db\"), &gorm.Config{})\r\n\tif err != nil {\r\n\t\treturn err\r\n\t}\r\n\terr = db.AutoMigrate(&Human{})\r\n\tif err != nil {\r\n\t\treturn err\r\n\t}\r\n\treturn nil\r\n}<\/pre>\nThe DBConnection<\/code> function is the auto migration function. The function returns an error if there\u2019s any during the migration process.<\/p>\nYou can proceed to call the DBConnection<\/code> function in the main<\/code> function.<\/p>\nfunc main() {\r\n\terr := DBConnection()\r\n\tif err != nil {\r\n\t\tlog.Fatal(\"Database connection error\", err)\r\n\t}\r\n\trouter := mux.NewRouter()\r\n\trouter.HandleFunc(\"\/humans\/{id}\", \r\n getHuman).Methods(\"GET\")\r\n\trouter.HandleFunc(\"\/humans\", createHuman).Methods(\"POST\")\r\n\trouter.HandleFunc(\"\/humans\/{id}\", \r\n updateHuman).Methods(\"PUT\")\r\n\trouter.HandleFunc(\"\/humans\/{id}\", \r\n deleteHuman).Methods(\"DELETE\")\r\n\tlog.Fatal(http.ListenAndServe(\":8080\", router))\r\n}<\/pre>\nThe next step is setting up the handler functions for successful operations.<\/p>\n
<\/a>The POST Request Handler Function<\/h2>\nYour POST request handler function would receive a JSON request body from the client, decode the JSON into the Human<\/code> struct instance and migrate the struct to the database using the Create<\/code> function of the database instance.<\/p>\nfunc createHuman(writer http.ResponseWriter, \r\n request *http.Request) {\r\n\tvar human Human\r\n\terr = json.NewDecoder(request.Body).Decode(&human)\r\n\tif err != nil {\r\n\t\tlog.Println(err)\r\n\t}\r\n\tdb.Create(&human)\r\n\terr := json.NewEncoder(writer).Encode(human)\r\n\tif err != nil {\r\n\t\tlog.Println(err)\r\n\t}\r\n}<\/pre>\nThe createHuman<\/code> handler function creates a handler function instance with HTTP response writer and requests instances as arguments, decodes the JSON to struct with the Decode<\/code> function of the NewDecoder<\/code> function, migrates the data to the database, and returns an encoded JSON struct to the client.<\/p>\nHere\u2019s a CURL request that makes a POST request to the server for the \/humans<\/code> route.<\/p>\ncurl -X POST -H \"Content-Type: application\/json\" \r\n -d '{\"name\":\"John Doe\",\"age\":30}' <http:\/\/localhost:8080\/humans> <\/pre>\n<\/a>The GET Request Handler Function<\/h2>\nYour GET<\/code> request handler function will receive an ID<\/code> from the client\u2019s request, search through the database for a row with the ID<\/code> and return the row’s data from the database as JSON.<\/p>\nfunc getHuman(writer http.ResponseWriter, request *http.Request) {\r\n\tvars := mux.Vars(request)\r\n\tid := vars[\"id\"]\r\n\tvar human Human\r\n\tdb.First(&human, id)\r\n\terr := json.NewEncoder(writer).Encode(human)\r\n\tif err != nil {\r\n\t\tlog.Println(err)\r\n\t}\r\n}<\/pre>\nThe getHuman<\/code> handler function accesses the data from the request using the Vars<\/code> function of the mux<\/code> package and retrieves the ID.<\/p>\nThe human<\/code> variable is an instance of the Human<\/code> struct created to hold the row’s data with the ID, and the Encode<\/code> function of the NewEncoder<\/code> function of the JSON package encodes the human<\/code> struct instance to the client as a response.<\/p>\nHere\u2019s the CURL request that makes a GET<\/code> to the server requesting data 1 as the ID.<\/p>\ncurl <http:\/\/localhost:8080\/humans\/1> <\/pre>\nHere\u2019s the result of the request. The request returns the data inserted into the database with the POST<\/code> request.<\/p>\n![](\"https:\/\/www.red-gate.com\/simple-talk\/wp-content\/uploads\/2023\/07\/word-image-97350-1-2.png\")
<\/p>\n
<\/a>The PUT Request Handler Function<\/h2>\nThe PUT<\/code> request handler function would retrieve an ID from the request URL<\/code> and a JSON payload from the request body and update the ID<\/code> row with the JSON from the request body.<\/p>\nfunc updateHuman(writer http.ResponseWriter, \r\n request *http.Request) {\r\n\tvars := mux.Vars(request)\r\n\tid := vars[\"id\"]\r\n\tvar human Human\r\n\tdb.First(&human, id)\r\n\terr := json.NewDecoder(request.Body).Decode(&human)\r\n\tif err != nil {\r\n\t\tlog.Println(err)\r\n\t}\r\n\tdb.Save(&human)\r\n\terr = json.NewEncoder(writer).Encode(human)\r\n\tif err != nil {\r\n\t\tlog.Println(err)\r\n\t}\r\n}<\/pre>\nThe updateHuman<\/strong> handler function extracts the ID from the request just like the GET request and retrieves the data with the ID from the database. If the retrieval is successful, the data exists. The Save<\/strong> function of the database instance updates the database with the JSON from the body of the request and returns the JSON to the client after successfully updating the database.<\/p>\nThe CURL request for the PUT request holds the payload with different name<\/strong> and age<\/strong> fields from the current data in the database with the ID of 1.<\/p>\ncurl -X PUT -H \"Content-Type: application\/json\" \r\n -d '{\"name\":\"Jane Doe\",\"age\":35}' <http:\/\/localhost:8080\/humans\/1><\/pre>\nOn sending the CURL request, here\u2019s the result of the update operation.<\/p>\n
![](\"https:\/\/www.red-gate.com\/simple-talk\/wp-content\/uploads\/2023\/07\/word-image-97350-2-2.png\")
<\/p>\n
<\/a>The DELETE Request Handler Function<\/h2>\nYour DELETE<\/code> request handler function would retrieve an ID<\/code> from the request and delete the row with the ID<\/code> from the database before responding to the client to signal a successful delete operation.<\/p>\nfunc deleteHuman(writer http.ResponseWriter, \r\n request *http.Request) {\r\n\tvars := mux.Vars(request)\r\n\tid := vars[\"id\"]\r\n\tdb.Delete(&Human{}, id)\r\n\t_, err := fmt.Fprintf(writer, \r\n \"Human with ID = %s has been deleted\", id)\r\n\tif err != nil {\r\n\t\tlog.Println(err)\r\n\t}\r\n} <\/pre>\nThe deleteHuman<\/code> function retrieves the ID from the client\u2019s request URL and deletes the row using the Delete<\/code> function of the database instance.<\/p>\nAfter a successful deletion operation, the function writes a string with the ID<\/code> to the client.<\/p>\n
![](\"https:\/\/www.red-gate.com\/simple-talk\/wp-content\/uploads\/2023\/07\/word-image-97350-3-2.png\")
<\/p>\n