Problem: You want to create a simple web service API that returns JSON.
Solution: Use the net/http package to create a web service API and the encoding/json package to encode data to be sent back as JSON.
You’ll create a web service API that returns a list of people in JSON format. You’ll use the net/http and chi packages to create the web service API and the encoding/json package to encode data to be sent back as JSON.
Start by creating a Person struct:
type Person struct { Name string `json:"name"` Height string `json:"height"` Mass string `json:"mass"` HairColor string `json:"hair_color"` SkinColor string `json:"skin_color"` EyeColor string `json:"eye_color"` BirthYear string `json:"birth_year"` Gender string `json:"gender"` } var list [] Person func init () { file , _ := os . Open ( "./datafiles/people.json" ) defer file . Close () data , _ := io . ReadAll ( file ) json . Unmarshal ( data , & list ) }
You use the init function to initialize the list variable with the data from the people.json file. This will be the data that you’ll return as JSON:
[ { "name" : "Luke Skywalker" , "height" : "172" , "mass" : "77" , "hair_color" : "blond" , "skin_color" : "fair" , "eye_color" : "blue" , "birth_year" : "19BBY" , "gender" : "male" }, { "name" : "C - 3PO" , "height" : "167" , "mass" : "75" , "hair_color" : "n/a" , "skin_color" : "gold" , "eye_color" : "yellow" , "birth_year" : "112BBY" , "gender" : "n/a" }, { "name" : "R2 - D2" , "height" : "96" , "mass" : "32" , "hair_color" : "n/a" , "skin_color" : "white, blue" , "eye_color" : "red" , "birth_year" : "33BBY" , "gender" : "n/a" } ]
Now you create a handler that uses the pattern "/people/{id}" to create a RESTful API that uses the path pattern /people/<id> :
func main () { mux := chi . NewRouter () mux . Get ( "/people/{id}" , people ) http . ListenAndServe ( ":8000" , mux ) } func people ( w http . ResponseWriter , r * http . Request ) { w . Header (). Set ( "Content-Type" , "application/json" ) idstr := chi . URLParam ( r , "id" ) id , err := strconv . Atoi ( idstr ) if err != nil { w . WriteHeader ( http . StatusBadRequest ) return } if id < 0 || id >= len ( list ) { w . WriteHeader ( http . StatusNotFound ) return } json . NewEncoder ( w ). Encode ( list [ id ]) }
First, set the Content - Type header to application/json . This tells the client that the response is in JSON format. Next, get the id from the URL path using the chi.URLParam function. If the id is not a number, you return a 400 Bad Request error. If the id is out of range, you return a 404 Not Found error.
