make test fails when GOPATH contains multiple paths

[lucasmundim]

Running make test when GOPATH contains multiple paths outputs an error message saying that moq tool is not found, although it is in fact installed.

$ echo $GOPATH
/Users/lucas.mundim/Projects/golang:/Users/lucas.mundim/.gvm/pkgsets/go1.10.8/global

$ ls /Users/lucas.mundim/.gvm/pkgsets/go1.10.8/global/bin/
moq

$ ls /Users/lucas.mundim/Projects/golang/bin/
moq

$ make test
Building for GOARCH=amd64
Everything is gofmt approved!
ERROR: 'moq' tool is needed to update mock test files, install it with:
go get github.com/matryer/moq

make: *** [pkg/controllers/proxy/network_services_controller_moq.go] Error 1