Bump up go and pkg version

Author: k1LoW

collector/collector.go

@@ -104,5 +104,5 @@ func detectOpenFileLimit() (int64, error) {
 	if err != nil {
 		return 0, err
 	}
-	return limits.OpenFiles, nil
+	return int64(limits.OpenFiles), nil
 }

go.mod

@@ -1,13 +1,16 @@
 module github.com/k1LoW/grouped_process_exporter
 
-go 1.13
+go 1.15
 
 require (
-	github.com/prometheus/client_golang v1.2.1
-	github.com/prometheus/client_model v0.0.0-20190812154241-14fe0d1b01d4
-	github.com/prometheus/common v0.7.0
-	github.com/prometheus/procfs v0.0.8
-	github.com/sirupsen/logrus v1.4.2
-	github.com/spf13/cobra v0.0.5
-	golang.org/x/sync v0.0.0-20190911185100-cd5d95a43a6e
+	github.com/alecthomas/units v0.0.0-20201120081800-1786d5ef83d4 // indirect
+	github.com/prometheus/client_golang v1.9.0
+	github.com/prometheus/client_model v0.2.0
+	github.com/prometheus/common v0.15.0
+	github.com/prometheus/procfs v0.3.0
+	github.com/sirupsen/logrus v1.7.0
+	github.com/spf13/cobra v1.1.1
+	golang.org/x/sync v0.0.0-20201207232520-09787c993a3a
+	golang.org/x/sys v0.0.0-20210124154548-22da62e12c0c // indirect
+	google.golang.org/protobuf v1.25.0 // indirect
 )