curl to Go

What this tool is used for

• Converting an API's curl example into net/http for a Go service.
• Reproducing a captured request inside an existing Go client.
• Getting the request construction and header setup right.
• Producing a snippet for a one-off command-line tool.
• Checking how a body is expressed as an io.Reader.

Frequently Asked Questions

Why must I close the response body?

defer resp.Body.Close() is mandatory. Go does not close it for you, and an unclosed body leaks the underlying connection so it never returns to the pool — under load this exhausts file descriptors. This is the most common bug in ported Go HTTP code.

Does http.Client have a default timeout?

No. The zero value means NO timeout, so a hung server blocks forever. Set client := &http.Client{Timeout: 10 * time.Second}, or use a context with context.WithTimeout for per-request control.

How do I send a JSON body?

Marshal to bytes and wrap in a reader: bytes.NewBuffer(payload) passed to http.NewRequest, then set req.Header.Set("Content-Type", "application/json"). Go will not infer the content type from the value.

How does curl's -k translate?

A custom transport: &http.Transport{TLSClientConfig: &tls.Config{InsecureSkipVerify: true}}. Note this disables verification for every request made through that client, not just one — build a separate client if you only need it for one host.

Does Go follow redirects automatically?

Yes, up to 10 by default — closer to curl -L than to bare curl. Override with the client's CheckRedirect func; returning http.ErrUseLastResponse stops following and hands you the 3xx directly.

How do I cancel a request?

With a context — `http.NewRequestWithContext` binds the request's lifetime to it, so cancelling the context aborts the in-flight call. That is the idiomatic mechanism; a client timeout is a blunter instrument covering the whole exchange.

Why reuse the Transport rather than the Client?

Because the `Transport` holds the connection pool. Creating a client per request with a fresh transport defeats keep-alive and leaks file descriptors under load — the default `http.DefaultTransport` is safe for concurrent use by design.

Common errors and gotchas

• Not closing `resp.Body`, which leaks connections — the deferred close is not optional.
• Using `http.DefaultClient`, which has no timeout at all and will hang forever.
• Setting a content-type after creating the request rather than on the request's header map.
• Assuming a non-2xx returns an error, when only a transport failure does.
• Reusing a request across retries, whose body has already been consumed.