Gin API Simulator

Handler

package main

import (
    "encoding/json"
    "fmt"
    "os"
)

type Payload struct {
    Name string `json:"name"`
}

func main() {
    var payload Payload
    _ = json.NewDecoder(os.Stdin).Decode(&payload)
    name := payload.Name
    if name == "" {
        name = "guest"
    }
    response := map[string]string{
        "status": "ok",
        "message": "Hello " + name,
        "framework": "Gin",
    }
    bytes, _ := json.MarshalIndent(response, "", "  ")
    fmt.Println(string(bytes))
}

Request Body (JSON)

Route Args (space separated)

Response

What Is the Gin API Simulator?

This tool lets you write Go code that mimics Gin-style API handler patterns and test JSON request/response handling directly in your browser. You provide a JSON request body, write a Go handler that processes it, and see the JSON response output instantly without installing Gin or running a local server.

The simulator focuses on the data-processing logic inside a Gin handler function. You can parse incoming JSON using Go's encoding/json package with struct tags, transform the data, and print a formatted JSON response. This is the same logic you would place inside a func(c *gin.Context) handler in a real Gin application.

All code runs on a remote sandboxed server powered by the Piston API. Your browser sends the Go source code and the JSON request body to the server, which compiles and executes the program inside an isolated container and returns the printed output as the simulated API response.

How It Works

Write your Go handler logic in the editor panel. The code reads a JSON request body from standard input, processes the data, and prints a JSON response to standard output.
Enter a JSON request body in the Request Body field. This simulates the payload that would be sent to a Gin API endpoint.
Add route arguments in the Route Args field if your handler expects path parameters such as a project ID or resource name.
Click the Run button to send your code and input to the execution server. The server compiles and runs the Go program with your JSON body provided through standard input.
View the response in the Response panel. The output shows whatever your handler prints, which is typically a formatted JSON response object.

Step-by-Step Example

Suppose you want to simulate a Gin handler that accepts a user's name and role, then returns a welcome message with permissions. Here is how to do it:

First, type the following code into the editor panel:

package main

import (
    "encoding/json"
    "fmt"
    "os"
)

type Request struct {
    Name string `json:"name"`
    Role string `json:"role"`
}

func main() {
    var req Request
    _ = json.NewDecoder(os.Stdin).Decode(&req)
    if req.Name == "" {
        req.Name = "guest"
    }
    if req.Role == "" {
        req.Role = "viewer"
    }

    response := map[string]interface{}{
        "status":  "ok",
        "message": "Welcome " + req.Name,
        "role":    req.Role,
        "framework": "Gin",
    }
    bytes, _ := json.MarshalIndent(response, "", "  ")
    fmt.Println(string(bytes))
}

Next, enter the following JSON in the Request Body field:

{"name": "Asha", "role": "admin"}

Now click the Run button. The server compiles and executes your Go handler with the provided JSON body. After a moment, the Response panel displays a JSON object with the welcome message and role information.

You can modify the request body or the handler logic and run again to test different scenarios, just as you would iterate on a real Gin handler function.

Use Cases

Learning Gin handler patterns. Understand how Gin handlers parse JSON request bodies and construct JSON responses without setting up a full Go project with Gin installed.
Prototyping API response logic. Quickly test data transformation and validation logic in Go before implementing it in a full Gin application.
Practicing JSON binding in Go. Experiment with json.Decoder, struct tags, json.MarshalIndent, and Go maps for building API response payloads.
Teaching REST API concepts. Demonstrate request/response cycles, handler patterns, and JSON formatting in a classroom or tutorial setting.
Testing edge cases. Verify how your handler logic responds to missing fields, empty bodies, or unexpected data types without deploying a Gin server.

Limitations and Notes

No real Gin server. This is a simulation. The Gin framework is not installed or running. You write handler logic in plain Go using the standard library.
No actual HTTP requests. The JSON body is passed through standard input, not through an HTTP request. Headers, cookies, and query parameters are not available.
No middleware. Gin middleware chains, logging middleware, and recovery middleware are not available in the sandbox.
No Go modules. External packages and Go modules are not available. Only Go's standard library packages can be imported.
No database access. There is no database in the sandbox. Simulate data with Go maps, slices, and structs instead.
Single file execution. Your entire handler must be in one Go file. Multi-file projects and package imports beyond the standard library are not supported.
Execution timeout applies. Programs that run too long or enter infinite loops are terminated automatically.

Frequently Asked Questions

Does this run a real Gin server?

No. This is a simulation that runs Go code to mimic Gin-style handler patterns. No actual Gin server or HTTP listener is started.

Does it make actual HTTP requests?

No. The simulator passes your JSON request body as standard input to a Go program. No real HTTP requests or net/http listeners are involved.

Does Gin middleware work here?

No. Gin middleware chains are not available in the sandbox. You write plain Go handler logic without middleware processing.

Do routing groups work?

Routing groups are shown as a simulated pattern for learning purposes. The tool does not process actual Gin router group definitions.

Can I connect to a database?

No. There is no database available in the sandbox. You can simulate data using Go maps and slices but cannot connect to any database.

Can I use Go modules or external packages?

No. Go modules and external packages are not available. Only Go's standard library packages can be imported.

What is the main use case for this tool?

It is designed for learning Gin-style API handler patterns, practicing JSON request and response handling in Go, and understanding how handlers process data.

Does JSON binding work?

JSON binding is simulated using Go's standard encoding/json package. You can unmarshal JSON into structs with json tags, which mirrors how Gin's ShouldBindJSON works.