Move internal/tools in its own module

Signed-off-by: Bogdan Drutu <[email protected]>

Makefile

@@ -45,6 +45,6 @@ lint:
 
 .PHONY: install-tools
 install-tools:
-	go install golang.org/x/tools/cmd/cover
-	go install github.com/golangci/golangci-lint/cmd/golangci-lint
+	cd internal/tools && go install golang.org/x/tools/cmd/cover
+	cd internal/tools && go install github.com/golangci/golangci-lint/cmd/golangci-lint
 

go.mod

@@ -1,13 +1,18 @@
 module contrib.go.opencensus.io/exporter/prometheus
 
 require (
-	github.com/golangci/golangci-lint v1.38.0
 	github.com/google/go-cmp v0.5.5
+	github.com/kr/text v0.2.0 // indirect
+	github.com/niemeyer/pretty v0.0.0-20200227124842-a10e7caefd8e // indirect
 	github.com/prometheus/client_golang v1.9.0
 	github.com/prometheus/statsd_exporter v0.20.0
+	github.com/sirupsen/logrus v1.8.0 // indirect
+	github.com/stretchr/testify v1.7.0 // indirect
 	go.opencensus.io v0.23.0
 	golang.org/x/sys v0.0.0-20210308170721-88b6017d0656 // indirect
-	golang.org/x/tools v0.1.0
+	golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1 // indirect
+	gopkg.in/check.v1 v1.0.0-20200227125254-8fa46927fb4f // indirect
+	gopkg.in/yaml.v2 v2.4.0 // indirect
 )
 
 go 1.13