Migrate to Go modules

Signed-off-by: Alex Ellis (OpenFaaS Ltd) <alexellis2@gmail.com>

gateway/vendor/github.com/prometheus/procfs/internal/util/parse.go

@@ -73,6 +73,15 @@ func ReadUintFromFile(path string) (uint64, error) {
 	return strconv.ParseUint(strings.TrimSpace(string(data)), 10, 64)
 }
 
+// ReadIntFromFile reads a file and attempts to parse a int64 from it.
+func ReadIntFromFile(path string) (int64, error) {
+	data, err := ioutil.ReadFile(path)
+	if err != nil {
+		return 0, err
+	}
+	return strconv.ParseInt(strings.TrimSpace(string(data)), 10, 64)
+}
+
 // ParseBool parses a string into a boolean pointer.
 func ParseBool(b string) *bool {
 	var truth bool