What version of Go are you using (go version)?

go version go1.8 darwin/amd64

What operating system and processor architecture are you using (go env)?

not really relevant but listed below:
GOARCH="amd64"
GOBIN=""
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="darwin"
GOOS="darwin"
GOPATH="/Users/puvvadip/Documents/work"
GORACE=""
GOROOT="/usr/local/go"
GOTOOLDIR="/usr/local/go/pkg/tool/darwin_amd64"
GCCGO="gccgo"
CC="clang"
GOGCCFLAGS="-fPIC -m64 -pthread -fno-caret-diagnostics -Qunused-arguments -fmessage-length=0 -fdebug-prefix-map=/var/folders/4r/1g2c4css78b1yn2q32dmqqm0l05w9h/T/go-build790682604=/tmp/go-build -gno-record-gcc-switches -fno-common"
CXX="clang++"
CGO_ENABLED="1"
PKG_CONFIG="pkg-config"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"

Issue

net/http's server documentation states

 // IdleTimeout is the maximum amount of time to wait for the
 // next request when keep-alives are enabled. If IdleTimeout
 // is zero, the value of ReadTimeout is used. If both are
 // zero, there is no timeout.
 IdleTimeout time.Duration

However, if no conn ReadDeadline is set because idleTimeout is zero at the bottom of the main loop of net/http.(*conn).serve (the relevant code is below)

    if d := c.server.idleTimeout(); d != 0 {
        c.rwc.SetReadDeadline(time.Now().Add(d))
        if _, err := c.bufr.Peek(4); err != nil {
            return
        }
    }
    c.rwc.SetReadDeadline(time.Time{})

Then the next iteration of the loop starts with

   w, err := c.readRequest(ctx)

Which starts with

  func (c *conn) readRequest(ctx context.Context) (w *response, err error) {
  	if c.hijacked() {
  		return nil, ErrHijacked
  	}
  
  	var (
  		wholeReqDeadline time.Time // or zero if none
  		hdrDeadline      time.Time // or zero if none
  	)
  	t0 := time.Now()
  	if d := c.server.readHeaderTimeout(); d != 0 {
  		hdrDeadline = t0.Add(d)
  	}
  	if d := c.server.ReadTimeout; d != 0 {
  		wholeReqDeadline = t0.Add(d)
  	}
  	c.rwc.SetReadDeadline(hdrDeadline)

Therefore in the case where both idleTimeout and readTimeout are not set, the readHeaderTimeout is used. The documentation for idleTimeout should state, “If both are zero, ReadHeaderTimeout is used.”