Open Swag Go Documentation

CORS Issues

Try-It Console Returns CORS Errors

Symptom: The try-it console shows CORS error or Failed to fetch when making requests.

Cause: Your API server doesn't include the correct CORS headers, or the browser blocks cross-origin requests from the docs UI to your API.

Solution: Configure CORS on your API server to allow requests from the docs origin:

import "github.com/rs/cors"
 
c := cors.New(cors.Options{
    AllowedOrigins:   []string{"https://docs.example.com"},
    AllowedMethods:   []string{"GET", "POST", "PUT", "DELETE", "OPTIONS"},
    AllowedHeaders:   []string{"Authorization", "Content-Type"},
    AllowCredentials: true,
})
 
handler := c.Handler(router)

Alternatively, configure a CORS proxy in the UI config:

docs := openswag.New(openswag.Config{
    Title:   "My API",
    Version: "1.0.0",
    UIConfig: openswag.UIConfig{
        CORSProxyURL: "https://cors-proxy.internal.example.com",
    },
})

Spec Generation Failures

Spec Generation Panics on Nil Pointer

Symptom: panic: runtime error: invalid memory address or nil pointer dereference when generating the spec.

Cause: An endpoint has a nil Response or RequestBody field that the generator tries to dereference.

Solution: Ensure all required fields are set on your endpoints:

docs.AddEndpoint(openswag.Endpoint{
    Method:  "GET",
    Path:    "/api/users",
    Summary: "List users",
    Response: openswag.Response{
        Status:      200,
        Description: "Success", // Don't leave this empty
        Body:        openswag.BodyFrom[[]User](),
    },
})

Struct Fields Not Appearing in Schema

Symptom: Some struct fields are missing from the generated OpenAPI schema.

Cause: Fields without a json struct tag or unexported fields are skipped by the schema generator.

Solution: Add json tags to all fields you want in the schema:

// Bad — Name is exported but has no json tag, ID is unexported
type User struct {
    id   string
    Name string
}
 
// Good
type User struct {
    ID   string `json:"id"`
    Name string `json:"name"`
}

Circular Reference in Schema

Symptom: maximum recursion depth exceeded or the spec generation hangs.

Cause: Your Go structs have circular references (e.g., User has a field of type *User).

Solution: Use pointer types for self-referencing fields. The schema generator handles *T by generating a $ref instead of inlining:

type TreeNode struct {
    Value    string      `json:"value"`
    Children []*TreeNode `json:"children,omitempty"`
}

Framework Mounting Problems

Chi: 404 on All Doc Routes

Symptom: Mounting with Chi returns 404 for /docs, /docs/openapi.json, etc.

Cause: Missing trailing wildcard in the route pattern.

Solution: Use the adapter's Mount function instead of manual mounting:

// Bad
r.Handle("/docs", docs.Handler())
 
// Good
import chiadapter "github.com/andrianprasetya/open-swag-go/adapters/chi"
chiadapter.Mount(r, "/docs", docs)

Gin: Conflicting Route Handlers

Symptom: panic: handlers are already registered for this path when mounting docs.

Cause: Another route conflicts with the docs wildcard route.

Solution: Use MountGroup to mount docs under a route group:

import ginadapter "github.com/andrianprasetya/open-swag-go/adapters/gin"
 
api := r.Group("/api")
ginadapter.MountGroup(api, "/docs", docs)

Fiber: Docs Page Loads But UI Is Blank

Symptom: The docs path returns HTML but the Scalar UI doesn't render.

Cause: Fiber's default content type handling may interfere with static asset serving.

Solution: Ensure the Fiber adapter is mounted correctly and static assets are served with proper MIME types:

import fiberadapter "github.com/andrianprasetya/open-swag-go/adapters/fiber"
 
fiberadapter.Mount(app, "/docs", docs)

If the issue persists, check that no middleware is modifying response headers for the /docs path.

Echo: Middleware Blocking Doc Routes

Symptom: Docs routes return 401 or 403 due to auth middleware.

Cause: Global auth middleware applies to the docs routes.

Solution: Mount docs before applying auth middleware, or use a group without the middleware:

import echoadapter "github.com/andrianprasetya/open-swag-go/adapters/echo"
 
// Mount docs first (no auth)
echoadapter.Mount(e, "/docs", docs)
 
// Then apply auth middleware to API routes
api := e.Group("/api", authMiddleware)

General Issues

Docs Work Locally But Not in Production

Symptom: Everything works on localhost but the docs page is blank or returns errors in production.

Cause: Common causes include reverse proxy stripping paths, missing environment variables, or HTTPS/HTTP mismatch.

Solution:

Check that your reverse proxy forwards the full path (including /docs/openapi.json)
Verify environment variables for DocsAuth credentials are set
Ensure the Server URL in your config matches the production URL:

docs := openswag.New(openswag.Config{
    Info: openswag.Info{
        Title:   "My API",
        Version: "1.0.0",
    },
    Servers: []openswag.Server{
        {URL: "https://api.example.com", Description: "Production"},
    },
})

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