golang/net

The golang.org/x/net/http2 package contains two different implementations of the HTTP/2 transport and server, and its behavior depends on your Go version:

1. The Original Implementation: This is the legacy implementation. It is used automatically if your Go version is less than 1.27.
2. The Wrapping Implementation: This is a reimplementation of the x/net/http2 APIs that wraps the standard library's net/http. It is used automatically if your Go version is 1.27 or higher.

Note: As of Go 1.27, the standard library package net/http/internal/http2 is the official source of truth for Go's HTTP/2 implementation. New features are developed there; x/net only receives critical bug and security fixes.

Once connected, you can use the following interactive features:

• Send raw frames: Send frames like PING or SETTINGS directly.
• HTTP/1.n to HTTP/2 conversion: Type standard HTTP/1.n headers and requests (e.g., GET / HTTP/1.1) and h2i will automatically HPACK and frame-ify them for HTTP/2.
• Tab completion: Use tab completion for commands and options.

Example usage:

h2i> PING h2iSayHI
h2i> headers
(as HTTP/1.1)> GET / HTTP/1.1
(as HTTP/1.1)> Host: example.com
(as HTTP/1.1)> 

Install the h2i interactive HTTP/2 console debugger using go install.

$ go install golang.org/x/net/http2/h2i@latest

Run h2i followed by the target hostname to start an interactive session. h2i allows you to send raw HTTP/2 frames (like PING or SETTINGS), type HTTP/1.n requests that are automatically converted to HTTP/2 frames, and view pretty-printed received frames with HPACK decoding.

$ h2i google.com

The server can initiate a graceful shutdown by sending a GOAWAY frame with the error code ErrCodeNo. This informs the client that the server is shutting down and no new streams should be created, while allowing existing streams to complete.

Note that a non-graceful shutdown (sending GOAWAY with an error code) will cause the connection to close after a timeout (defaulting to 1 * time.Second) to allow the client to receive the GOAWAY frame and avoid immediate TCP RSTs.

The http2.Server struct allows you to customize the behavior of the HTTP/2 implementation. Key configuration areas include:

• Timeouts: IdleTimeout and ReadTimeout can be inherited from the base http.Server or set explicitly.
• Flow Control: MaxUploadBufferPerStream and MaxUploadBufferPerConnection control the window sizes for flow control.
• Concurrency: MaxConcurrentStreams sets the limit for concurrent streams advertised to the client.
• Security: PermitProhibitedCipherSuites (boolean) allows or disallows certain cipher suites.
• Error Tracking: CountError is a function hook for tracking HTTP/2 error types.
• Ping/Idle Management: PingTimeout controls how long the server waits for a PING response before closing the connection.

The h2i command-line tool accepts the following flags:

• -insecure: Whether to skip TLS cert validation.
• -nextproto string: Comma-separated list of NPN/ALPN protocol names to negotiate. (default "h2,h2-14").