Why Does My Go HTTP Server Return Empty JSON Responses?

JSON Responses in Go: Resolving Issues with Empty Replies

In Go, constructing HTTP responses with JSON content can pose challenges, particularly when dealing with null results. This article aims to address a common issue faced while attempting to produce JSON responses.

Problem Statement

A beginner in Go is attempting to implement a simple HTTP server with JSON response functionality. However, the server consistently returns an empty response with a "text/plain; charset=utf-8" content-type. The developer has compared their code to an online example but fails to identify any differences.

Solution

The crux of the issue lies in the visibility of the struct's fields. In Go, struct fields must be exported (uppercase) to be accessible for JSON marshaling.

Example Code (Original/Incorrect):

<code class="go">type ResponseCommands struct {
    key   string
    value bool
}</code>

Example Code (Corrected):

<code class="go">type ResponseCommands struct {
    Key   string
    Value bool
}</code>

When the fields are exported, the JSON encoder can properly access and encode their values. This simple yet critical change resolves the issue and allows the server to return valid JSON responses.

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