This issue occurs with the latest Go version (1.6 darwin/amd64) and on master.

When net.DialTimeout is passed a very large timeout argument like 1 << 63 - 1, the call returns immediately with the error i/o timeout. I expected the call to block indefinitely.

I have a repro test:
https://github.com/prashantv/dial-timeout-repro

The issue seems to be in runtime.setDeadlineImpl:

d := runtimeNano() + int64(t.Sub(time.Now()))

This can overflow the int64 and result in a negative number. I'm also not sure whether this line needs to call runtimeNano and time.Now. The current code converts t to an int64 representing the unix nanos, but this can be done by calling t.UnixNano which will be clearer and cheaper.

I'm working on a CL to fix this.