regexp: Regex returns true for strings that it should not match

[arunvm123]

Please answer these questions before submitting your issue. Thanks!

What did you do?

Tried to construct a regex pattern that matches whitespaces between words, so as to validate names. The pattern should match only letters and whitespaces but seems to return true for other characters as well.

https://play.golang.org/p/3LoX8_haM_6

What did you expect to see?

The program to return false

What did you see instead?

The program returned true

Does this issue reproduce with the latest release (go1.9.4)?

System details

go version go1.9 linux/amd64
GOARCH="amd64"
GOBIN="/home/arunvm/go/bin"
GOEXE=""
GOHOSTARCH="amd64"
GOHOSTOS="linux"
GOOS="linux"
GOPATH="/home/arunvm/go"
GORACE=""
GOROOT="/usr/local/go"
GOTOOLDIR="/usr/local/go/pkg/tool/linux_amd64"
GCCGO="gccgo"
CC="gcc"
GOGCCFLAGS="-fPIC -m64 -pthread -fmessage-length=0 -fdebug-prefix-map=/tmp/go-build814277393=/tmp/go-build -gno-record-gcc-switches"
CXX="g++"
CGO_ENABLED="1"
CGO_CFLAGS="-g -O2"
CGO_CPPFLAGS=""
CGO_CXXFLAGS="-g -O2"
CGO_FFLAGS="-g -O2"
CGO_LDFLAGS="-g -O2"
PKG_CONFIG="pkg-config"
GOROOT/bin/go version: go version go1.9 linux/amd64
GOROOT/bin/go tool compile -V: compile version go1.9
uname -sr: Linux 4.11.12-100.fc24.x86_64
LSB Version:	:core-4.1-amd64:core-4.1-noarch:cxx-4.1-amd64:cxx-4.1-noarch:desktop-4.1-amd64:desktop-4.1-noarch:languages-4.1-amd64:languages-4.1-noarch:printing-4.1-amd64:printing-4.1-noarch
Distributor ID:	Fedora
Description:	Fedora release 24 (Twenty Four)
Release:	24
Codename:	TwentyFour
/lib64/libc.so.6: GNU C Library (GNU libc) stable release version 2.23, by Roland McGrath et al.
gdb --version: GNU gdb (GDB) Fedora 7.11.1-86.fc24

[mvdan]

You're missing the $ at the end, otherwise you get a partial match: https://play.golang.org/p/FJrDA4jlNHE

Always assume that the error is in your code before thinking there is a bug in the standard library. You should also try the forums to ask questions first: https://golang.org/wiki/Questions.