net/http: Setting r.Close = true in a handler does not cause the server to close the connection

[johnmaguire]

Go version

go version go1.23.4 darwin/arm64

Output of go env in your module/workspace:

GO111MODULE=''
GOARCH='arm64'
GOBIN=''
GOCACHE='/Users/jmaguire/Library/Caches/go-build'
GOENV='/Users/jmaguire/Library/Application Support/go/env'
GOEXE=''
GOEXPERIMENT=''
GOFLAGS=''
GOHOSTARCH='arm64'
GOHOSTOS='darwin'
GOINSECURE=''
GOMODCACHE='/Users/jmaguire/go/pkg/mod'
GONOPROXY='github.com/DefinedNet'
GONOSUMDB='github.com/DefinedNet'
GOOS='darwin'
GOPATH='/Users/jmaguire/go'
GOPRIVATE='github.com/DefinedNet'
GOPROXY='https://proxy.golang.org,direct'
GOROOT='/opt/homebrew/Cellar/go/1.23.4/libexec'
GOSUMDB='sum.golang.org'
GOTMPDIR=''
GOTOOLCHAIN='local'
GOTOOLDIR='/opt/homebrew/Cellar/go/1.23.4/libexec/pkg/tool/darwin_arm64'
GOVCS=''
GOVERSION='go1.23.4'
GODEBUG=''
GOTELEMETRY='local'
GOTELEMETRYDIR='/Users/jmaguire/Library/Application Support/go/telemetry'
GCCGO='gccgo'
GOARM64='v8.0'
AR='ar'
CC='cc'
CXX='c++'
CGO_ENABLED='1'
GOMOD='/Users/jmaguire/src/junkcode/read-deadline-empty-body/go.mod'
GOWORK=''
CGO_CFLAGS='-O2 -g'
CGO_CPPFLAGS=''
CGO_CXXFLAGS='-O2 -g'
CGO_FFLAGS='-O2 -g'
CGO_LDFLAGS='-O2 -g'
PKG_CONFIG='pkg-config'
GOGCCFLAGS='-fPIC -arch arm64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -ffile-prefix-map=/var/folders/2t/rbxbv8612sq9_rdrxhtw8rzc0000gn/T/go-build893276654=/tmp/go-build -gno-record-gcc-switches -fno-common'

What did you do?

Issue two requests against a handler that sets r.Close = true: https://go.dev/play/p/1OVTsaO82br

What did you see happen?

Both requests used the same connection (see "Remote address" and "Close" flag on the client.)

What did you expect to see?

The server close the connection to the client per the Request docs:

// Close indicates whether to close the connection after
// replying to this request (for servers) or after sending this
// request and reading its response (for clients).

The docs do state the following:

// For server requests, the HTTP server handles this automatically
// and this field is not needed by Handlers.

The wording here ("not needed") implies that handlers can access it, but do not need to. In our case, we wanted to explicitly close the HTTP connection. Setting this flag did not achieve that. Setting r.Header().Set("Connection", "close") did.

[gabyhelp]

Related Issues

• x/net/http2: setting Request.Close doesn't close TCP connections #49375 (closed)
• net/http, x/net/http2: TCP connection is not closed after http client request times out after missing RST (TCP) or GOAWAY(HTTP/2) frame #36026
• net/http: TCP connection is not closed after http client makes a https request via a http proxy server which doesn't response #28012 (closed)
• net/http: Response.Write adds redundant "Connection: Close" headers #19499 (closed)
• net/http: Server still handling new connections after Close (or Shutdown) returns #36093 (closed)
• net/http, x/net/http2: http server shutdown doesn't gracefully shut down HTTP2 connections #39776 (closed)
• net/http: Errors from persistConn.readLoop not returned to client still writing a request #62447
• net/http: request.Body.Close can be called more than once #40382 (closed)

Related Code Changes

• net/http: close connection if `Connection: close` is set

Related Discussions

• Calling Close() on http.Request.Body

_{(Emoji vote if this was helpful or unhelpful; more detailed feedback welcome in this discussion.)}

[chad-bekmezian-snap]

I believe this is expected behavior, but poorly worded documentation

[seankhliao]

The docs for http.Handler explicitly state that handlers should not modify the request. I don't think we need to reducument that for every field.

[johnmaguire]

Thanks @seankhliao - the phrasing "this field is not needed by Handlers" is what threw me off here. Something to the effect of "Changing this field from Handlers has no effect" might be more helpful.