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

$ go version
go version go1.10.3 windows/amd64

Does this issue reproduce with the latest release?

this is related to documentation

net.Conn.setDeadline says:

The deadline applies to all future and pending I/O, 
not just the immediately following call to ReadFrom 
or WriteTo

This means I can extend previously set deadline to longer period.

but when i look at nettest.testPresentTimeout it says:

testPresentTimeout tests that a deadline set while there are pending
Read and Write operations immediately times out those operations.

if so, net.Conn.SetDeadline should say that:
changing timeout will cause any pending I/O calls to timeout

By looking at nettest.testPresentTimeout code, I see that it is not extending current deadline. so
test is correct but its doc is wrong. I tried to see if there is any test, which tests extending deadline of
pending IO, but could not find

for clarification, i checked net.Pipe implementation:

any pending net.pipe.Read will always timeout on setDeadline
any pending net.pipe.Write may sometimes timeout on setDeadline and sometime not (if setDeadline called between for loop iterations