zip/docs/MIGRATION.md

Migration guide

zip ships drop-in adapters for chi, gin, beego, and stdlib net/http. Each adapter is documented as a migration tool — they exist so a service can roll onto zip incrementally. Adapter dispatch costs ~5% versus native Fiber routing; replace adapted routes with native zip handlers when feasible.

From gin

gin handlers take *gin.Context; zip handlers take *zip.Ctx. The shapes are deliberately close.

// gin
r := gin.Default()
r.GET("/users/:id", func(c *gin.Context) {
    c.JSON(200, gin.H{"id": c.Param("id")})
})

// zip
app := zip.New(zip.Config{})
app.Get("/users/:id", func(c *zip.Ctx) error {
    return c.JSON(200, map[string]string{"id": c.Param("id")})
})

Common mappings:

gin	zip
gin.H{...}	map[string]any{...} or a typed struct
c.Param("id")	c.Param("id")
c.Query("q")	c.Query("q")
c.GetHeader("X-Foo")	c.Header("X-Foo")
c.BindJSON(&v)	c.Bind(&v)
c.AbortWithStatusJSON(400, ...)	return zip.ErrBadRequest("...")
gin.Recovery()	middleware.Recover()
gin.Logger()	middleware.Logger(app.Logger())

For routes that are too complex to port today, mount the gin engine as a legacy adapter:

gin := buildExistingGinApp()
app.Mount("/legacy/gin", gin)

From chi

chi routers implement http.Handler, so zip.AdaptNetHTTP works unchanged.

chiRouter := chi.NewRouter()
chiRouter.Get("/users", listUsers)

app := zip.New(zip.Config{})
app.Mount("/legacy/chi", chiRouter)

Common mappings:

chi	zip
chi.NewRouter()	zip.New(zip.Config{})
r.Route("/v1", fn)	app.Route("/v1", fn)
r.Group(fn)	app.Group("/", h1, h2)
chi.URLParam(r, "id")	c.Param("id")
middleware (func(http.Handler) http.Handler)	middleware.AdaptNetHTTPMiddleware(mw)

From beego

beego *web.HttpServer exposes its handler chain via BeeApp.Handlers, which is an http.Handler. Mount it via app.Mount.

import "github.com/beego/beego/v2/server/web"

beeApp := web.NewHttpServer()
// ... existing beego config

app := zip.New(zip.Config{})
app.Mount("/legacy/iam", beeApp.Handlers)

Notes:

• beego's auto-routing magic (controllers reflected from struct names) has no zip equivalent — port to native zip handlers when feasible.
• beego's app.conf and beego-specific filters do not carry over; re-implement filters as zip middleware.

From net/http

The zero-config path: any http.Handler works.

existing := http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
    w.Write([]byte("hello"))
})
app.Mount("/legacy", existing)

For middleware that takes func(http.Handler) http.Handler:

mw := func(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        w.Header().Set("X-Custom", "1")
        next.ServeHTTP(w, r)
    })
}
app.Use(zip.AdaptNetHTTPMiddleware(mw))

Replacing adapters with native handlers

Once a route's traffic warrants it, rewrite from Mount to native zip:

// before
app.Mount("/legacy/chi", chiRouter)

// after (per-route migration)
v1 := app.Group("/v1")
v1.Get("/users", listUsers)        // was chiRouter.Get("/users", ...)
v1.Post("/users", createUser)

The ~5% perf delta compounds at high RPS and the adapter chain is a sharp edge for debugging — native handlers see fiber.Ctx directly, adapters bounce through fasthttp ↔ net/http translation.