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Repair Windows errors before they cause bigger problemsFix Now →Fix the driver behind crashes, sound loss and screen glitchesFind Drivers →Clear out junk files and repair common Windows errorsFree Scan →To build an API with Go, create a module, define resource-shaped endpoints, decode and encode JSON, return deliberate HTTP status codes, and connect handlers to persistent storage. The smallest useful example can run with either the Gin framework or Go 1.22+ net/http. Start with an in-memory service to understand the request flow, then replace that slice with a database and add the operational controls your application requires.
What you will build
This tutorial creates an album API with three endpoints:
| Method | Path | Purpose | Success response |
|---|---|---|---|
| GET | /albums | List all albums | 200 with a JSON array |
| POST | /albums | Create an album | 201 with the created object |
| GET | /albums/{id} | Fetch one album | 200 with an object, or 404 |
The data is held in memory so the example stays focused. It disappears when the process stops; a real application normally reads and writes a database.
Prerequisites and project setup
- Install a current Go toolchain. The standard-library routing used later requires Go 1.22 or newer.
- Know basic Go syntax, structs, slices, pointers, and error handling.
- Have
curlor another HTTP client for testing.
- Create a directory and initialize a module (replace the module path with your repository path):
mkdir go-albums cd go-albums go mod init example.com/go-albums - If using Gin, add it to the module:
go get github.com/gin-gonic/gin - Create
main.go, then run the server withgo run ..
Define the resource and API contract
Use a JSON-friendly struct and stable field names. Keep the identifier as a string at the HTTP boundary so clients do not depend on an internal numeric type.
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type album struct {
ID string `json:"id"`
Title string `json:"title"`
Artist string `json:"artist"`
Price float64 `json:"price"`
}
type createAlbum struct {
Title string `json:"title"`
Artist string `json:"artist"`
Price float64 `json:"price"`
}Decide validation rules before writing handlers: title and artist are required, price must not be negative, and an unknown ID is a 404. Returning consistent JSON errors makes clients easier to write.
Build the API with Gin
Gin is the framework used by the official Go REST tutorial. It supplies route matching, JSON binding, and response helpers while leaving your application logic in ordinary Go functions.
package main
import (
"net/http"
"github.com/gin-gonic/gin"
)
type album struct {
ID string `json:"id"`
Title string `json:"title"`
Artist string `json:"artist"`
Price float64 `json:"price"`
}
type createAlbum struct {
Title string `json:"title" binding:"required"`
Artist string `json:"artist" binding:"required"`
Price float64 `json:"price" binding:"gte=0"`
}
var albums = []album{
{ID: "1", Title: "Blue Train", Artist: "John Coltrane", Price: 56.99},
{ID: "2", Title: "Jeru", Artist: "Gerry Mulligan", Price: 17.99},
}
func listAlbums(c *gin.Context) {
c.JSON(http.StatusOK, albums)
}
func createAlbumHandler(c *gin.Context) {
var input createAlbum
if err := c.ShouldBindJSON(&input); err != nil {
c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
return
}
nextID := "3" // Replace with a database-generated ID in a real service.
created := album{ID: nextID, Title: input.Title, Artist: input.Artist, Price: input.Price}
albums = append(albums, created)
c.JSON(http.StatusCreated, created)
}
func getAlbum(c *gin.Context) {
id := c.Param("id")
for _, a := range albums {
if a.ID == id {
c.JSON(http.StatusOK, a)
return
}
}
c.JSON(http.StatusNotFound, gin.H{"error": "album not found"})
}
func main() {
router := gin.Default()
router.GET("/albums", listAlbums)
router.POST("/albums", createAlbumHandler)
router.GET("/albums/:id", getAlbum)
router.Run(":8080")
}Run it with go run .. Gin listens on port 8080. In a second terminal:
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curl http://localhost:8080/albums
curl http://localhost:8080/albums/1
curl -i -X POST http://localhost:8080/albums
-H 'Content-Type: application/json'
-d '{"title":"Kind of Blue","artist":"Miles Davis","price":39.99}'The POST should return 201. Malformed JSON or a missing required field returns 400; an absent ID returns 404.
Preventing duplicate IDs
The fixed nextID is intentionally educational and will collide after the first creation. In production, let the database generate a primary key or use a collision-resistant ID generator. Also protect shared in-memory state with synchronization if handlers can write concurrently; a database transaction is the usual durable solution.
Use Go 1.22+ net/http instead of a framework
Go 1.22 added method matching and wildcard segments to http.ServeMux. A wildcard can be read with Request.PathValue. The Go team describes this as “one fewer dependency for many projects,” while noting that third-party frameworks remain appropriate for advanced routing needs.
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package main
import (
"encoding/json"
"fmt"
"log"
"net/http"
)
type album struct { ID string `json:"id"`; Title string `json:"title"`; Artist string `json:"artist"`; Price float64 `json:"price"` }
var albums = []album{{"1", "Blue Train", "John Coltrane", 56.99}}
func writeJSON(w http.ResponseWriter, status int, value any) {
w.Header().Set("Content-Type", "application/json")
w.WriteHeader(status)
_ = json.NewEncoder(w).Encode(value)
}
func main() {
mux := http.NewServeMux()
mux.HandleFunc("GET /albums", func(w http.ResponseWriter, r *http.Request) { writeJSON(w, http.StatusOK, albums) })
mux.HandleFunc("GET /albums/{id}", func(w http.ResponseWriter, r *http.Request) {
id := r.PathValue("id")
for _, a := range albums { if a.ID == id { writeJSON(w, http.StatusOK, a); return } }
writeJSON(w, http.StatusNotFound, map[string]string{"error": "album not found"})
})
mux.HandleFunc("POST /albums", func(w http.ResponseWriter, r *http.Request) {
var input album
dec := json.NewDecoder(r.Body)
if err := dec.Decode(&input); err != nil { writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid JSON"}); return }
input.ID = fmt.Sprintf("%d", len(albums)+1)
albums = append(albums, input)
writeJSON(w, http.StatusCreated, input)
})
log.Println("listening on :8080")
log.Fatal(http.ListenAndServe(":8080", mux))
}Choose net/http when method-and-path routing plus your own middleware is enough. Choose Gin (or another framework) when you need its binding, middleware ecosystem, grouping, or more elaborate routing abstractions. Go 1.22 routing removes a dependency; it does not remove every reason to use a framework.
JSON, validation, and HTTP behavior
Decode safely
Use a request-specific input struct instead of decoding directly into a persistence model. Set a body limit with http.MaxBytesReader in a standard-library handler, reject trailing JSON values when strictness matters, and close request bodies that you open yourself.
Return predictable statuses
- 200 OK: successful reads and updates that return a representation.
- 201 Created: successful creation; include the representation and, where useful, a
Locationheader. - 204 No Content: successful deletion or an update with no response body.
- 400 Bad Request: malformed JSON or invalid field values.
- 404 Not Found: the route or resource does not exist.
- 409 Conflict: a uniqueness or state conflict.
- 500 Internal Server Error: an unexpected server failure; do not expose stack traces or database details.
Keep errors machine-readable
Use one shape, such as {"error":"album not found"}, across handlers. Log the detailed cause on the server while returning a safe message to the client.
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Replace the slice with persistent storage
The official Gin example explicitly treats its slice as a simplification; a typical API interacts with a database. Create a repository layer so handlers depend on methods such as ListAlbums, FindAlbum, and CreateAlbum, not SQL strings. Open a connection pool at startup, configure its limits and lifetime, use context-aware queries, and close the pool during graceful shutdown. Wrap multi-step writes in transactions and map “no rows” to 404 rather than 500. Keep migrations versioned with the application.
Run and test the service
- Format and compile:
gofmt -w .thengo test ./.... - Run locally with
go run .and exercise every success and error path usingcurl. - Add table-driven unit tests for validation and handler responses. Use
httptestto test without opening a real port. - Add integration tests against a disposable database before relying on repository behavior.
Keep configuration such as the listen address, database URL, and logging level in environment variables or a configuration object rather than hard-coding secrets.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Production concerns the small example does not solve
An API is not production-ready merely because it returns JSON. Define authentication and authorization separately: identifying a caller is not the same as deciding what that caller may do. Enforce TLS at the deployment boundary, validate and bound every input, apply request timeouts, and decide how rate limiting and pagination fit your traffic. Add structured logs, metrics, traces, health endpoints, and alerts appropriate to your service. The tutorial sources establish the implementation path, not a complete security or operations checklist, so document these decisions for your environment and threat model.
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Graceful shutdown
Use an http.Server with read, write, and idle timeouts. On shutdown, stop accepting new requests, give in-flight requests a bounded grace period, then close database resources. This prevents deploys from cutting off active clients.
Common failures and fixes
| Symptom | Likely cause | Fix |
|---|---|---|
404 for a valid-looking URL |
Method or path pattern does not match. | Check the HTTP verb, leading slash, wildcard name, and Go version when using ServeMux. |
400 on a POST |
Invalid JSON, wrong content type, or missing required field. | Send Content-Type: application/json and validate the exact payload. |
| Server exits immediately | ListenAndServe or router.Run returned an error. |
Log the returned error; check whether port 8080 is already occupied. |
| New records vanish | Storage is the demonstration slice. | Persist records in a database and load them on startup. |
| Duplicate IDs under load | IDs are generated from slice length. | Use a database sequence or collision-resistant IDs. |
| Data races reported by tests | Concurrent handlers mutate shared memory. | Run go test -race ./...; add synchronization or move writes to a transactional store. |
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require('fs').writeFileSync('shot.webp', Buffer.from(await res.arrayBuffer()));Frequently Asked Questions
Should a new Go API start with Gin or net/http?
Use net/http when method-and-path routing is sufficient; use Gin when its binding, middleware, grouping, or broader framework abstractions provide value. Both are valid choices.
Why does my in-memory API lose data after a restart?
The sample stores records in a process-local slice. Replace that slice with a database-backed repository for durable data.
What Go version supports wildcard values in ServeMux?
Go 1.22 introduced method patterns, wildcard path segments, and Request.PathValue in the standard router.
The Bottom Line
A sound Go API begins with a small, tested contract and clear handlers, then grows behind repository, validation, authentication, observability, and deployment boundaries. Use Gin for convenient framework features or Go 1.22+ net/http for a dependency-light router, but do not mistake the in-memory tutorial for a production architecture.
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