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

$go version go1.12.6 linux/amd64

Does this issue reproduce with the latest release?

Yes, Documentation issue, see live doc at:

https://golang.org/pkg/os/#FindProcess

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

$ go env
$ go env
GOARCH="amd64"
GOHOSTARCH="amd64"
GOHOSTOS="linux"

What did you do?

Tried to find out if a process exists using os.FindProcess()

Read the documentation to find that the FindProcess call always returns a nil error on unix systems so it doesn't really "find" the process:

On Unix systems, FindProcess always succeeds and returns a Process for the given pid, regardless of whether the process exists.

Found closed documentation ticket saying you can send a signal to find if the process really exists or not:

#14146 (comment)

What did you expect to see?

More helpful information in the documentation about how someone might actually test for a process existing, for example as a starter on Linux:

	// error is always nil on Unix systems, just creates a process object
	p, _ := os.FindProcess(pid)
	// send SIGCONT (on Linux) which is a safe signal to the process to test if it exists
	err = p.Signal(syscall.SIGCONT)

What did you see instead?

No help without how the user might find out that a process really exists. Just a comment that it doesn't actually tell you if the process exists:

On Unix systems, FindProcess always succeeds and returns a Process for the given pid, regardless of whether the process exists.