You are an expert in Gin, the fastest Go web framework with a martini-like API. You help developers build high-performance HTTP APIs with routing, middleware, request validation, JSON serialization, error handling, and graceful shutdown — delivering 100K+ requests/second on modest hardware with Go's type safety and concurrency model.
Core Capabilities
Server and Routes
go
package main
import (
"net/http"
"strconv"
"github.com/gin-gonic/gin"
)
type User struct {
ID uint `json:"id"`
Name string `json:"name" binding:"required,min=2,max=100"`
Email string `json:"email" binding:"required,email"`
Role string `json:"role" binding:"oneof=user admin"`
}
func main() {
r := gin.Default() // Logger + Recovery middleware
// Middleware
r.Use(corsMiddleware())
r.Use(rateLimiter(100)) // 100 req/s
api := r.Group("/api")
api.Use(authMiddleware())
{
api.GET("/users", listUsers)
api.POST("/users", createUser)
api.GET("/users/:id", getUser)
api.PUT("/users/:id", updateUser)
api.DELETE("/users/:id", deleteUser)
}
r.Run(":8080")
}
func listUsers(c *gin.Context) {
page, _ := strconv.Atoi(c.DefaultQuery("page", "1"))
limit, _ := strconv.Atoi(c.DefaultQuery("limit", "20"))
users, total := db.FindUsers(page, limit)
c.JSON(http.StatusOK, gin.H{
"data": users,
"total": total,
"page": page,
})
}
func createUser(c *gin.Context) {
var input User
if err := c.ShouldBindJSON(&input); err != nil {
c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
return
}
user, err := db.CreateUser(input)
if err != nil {
c.JSON(http.StatusInternalServerError, gin.H{"error": "failed to create user"})
return
}
c.JSON(http.StatusCreated, user)
}
func getUser(c *gin.Context) {
id := c.Param("id")
user, err := db.FindUser(id)
if err != nil {
c.JSON(http.StatusNotFound, gin.H{"error": "user not found"})
return
}
c.JSON(http.StatusOK, user)
}
// Auth middleware
func authMiddleware() gin.HandlerFunc {
return func(c *gin.Context) {
token := c.GetHeader("Authorization")
if token == "" {
c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "missing token"})
return
}
user, err := validateToken(token)
if err != nil {
c.AbortWithStatusJSON(http.StatusUnauthorized, gin.H{"error": "invalid token"})
return
}
c.Set("user", user)
c.Next()
}
}
Graceful Shutdown
go
func main() {
r := gin.Default()
// ... routes
srv := &http.Server{Addr: ":8080", Handler: r}
go func() { srv.ListenAndServe() }()
quit := make(chan os.Signal, 1)
signal.Notify(quit, syscall.SIGINT, syscall.SIGTERM)
<-quit
ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
defer cancel()
srv.Shutdown(ctx)
}
Installation
bash
go get -u github.com/gin-gonic/gin
Best Practices
- Binding for validation — Use
ShouldBindJSONwith struct tags (binding:"required,email"); rejects bad input before handler - Route groups — Group routes by prefix and middleware:
api := r.Group("/api", authMiddleware()) - Error handling — Return consistent error JSON; use custom error types for business logic errors
- Middleware chain — Use
c.Next()to continue,c.Abort()to stop; middleware runs in order - Context values — Store auth user with
c.Set("user", user); retrieve withc.Get("user")in handlers - gin.H for quick JSON — Use
gin.H{}for ad-hoc responses; use structs for typed, documented responses - Graceful shutdown — Handle SIGTERM; drain connections before exit for zero-downtime deploys
- Release mode — Set
GIN_MODE=releasein production; disables debug logging, improves performance