Bump minumim required Go version to 1.13

Since 1.16 is out, we still support the last four minor releases.

The bump was required by the prometheus/procfs package using the new
`%w` printf directives. However, it also allows us to remove some
special casing about build info.

Signed-off-by: beorn7 <beorn@grafana.com>

.circleci/config.yml

@@ -50,22 +50,6 @@ workflows:
   client_golang:
     jobs:
     # Refer to README.md for the currently supported versions.
-    - test:
-        name: go-1-9
-        go_version: "1.9"
-        use_gomod_cache: false
-    - test:
-        name: go-1-10
-        go_version: "1.10"
-        use_gomod_cache: false
-    - test:
-        name: go-1-11
-        go_version: "1.11"
-        run_lint: true
-    - test:
-        name: go-1-12
-        go_version: "1.12"
-        run_lint: true
     - test:
         name: go-1-13
         go_version: "1.13"
@@ -78,6 +62,10 @@ workflows:
         name: go-1-15
         go_version: "1.15"
         run_lint: true
+    - test:
+        name: go-1-16
+        go_version: "1.16"
+        run_lint: true
         # Style and unused/missing packages are only checked against
         # the latest supported Go version.
         run_style_and_unused: true

README.md

@@ -9,7 +9,7 @@ This is the [Go](http://golang.org) client library for
 instrumenting application code, and one for creating clients that talk to the
 Prometheus HTTP API.
 
-__This library requires Go1.9 or later.__ The minimum required patch releases for older Go versions are Go1.9.7 and Go1.10.3.
+__This library requires Go1.13 or later.__
 
 ## Important note about releases and stability
 

go.mod

@@ -11,4 +11,4 @@ require (
 	golang.org/x/sys v0.0.0-20210309074719-68d13333faf2
 )
 
-go 1.11
+go 1.13

prometheus/build_info.go

@@ -1,29 +0,0 @@
-// Copyright 2019 The Prometheus Authors
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-// http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-// +build go1.12
-
-package prometheus
-
-import "runtime/debug"
-
-// readBuildInfo is a wrapper around debug.ReadBuildInfo for Go 1.12+.
-func readBuildInfo() (path, version, sum string) {
-	path, version, sum = "unknown", "unknown", "unknown"
-	if bi, ok := debug.ReadBuildInfo(); ok {
-		path = bi.Main.Path
-		version = bi.Main.Version
-		sum = bi.Main.Sum
-	}
-	return
-}

prometheus/build_info_pre_1.12.go

@@ -1,22 +0,0 @@
-// Copyright 2019 The Prometheus Authors
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-// http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
-
-// +build !go1.12
-
-package prometheus
-
-// readBuildInfo is a wrapper around debug.ReadBuildInfo for Go versions before
-// 1.12. Remove this whole file once the minimum supported Go version is 1.12.
-func readBuildInfo() (path, version, sum string) {
-	return "unknown", "unknown", "unknown"
-}

prometheus/go_collector.go

@@ -384,7 +384,12 @@ type memStatsMetrics []struct {
 // https://github.com/povilasv/prommod for an example of a collector for the
 // module dependencies.
 func NewBuildInfoCollector() Collector {
-	path, version, sum := readBuildInfo()
+	path, version, sum := "unknown", "unknown", "unknown"
+	if bi, ok := debug.ReadBuildInfo(); ok {
+		path = bi.Main.Path
+		version = bi.Main.Version
+		sum = bi.Main.Sum
+	}
 	c := &selfCollector{MustNewConstMetric(
 		NewDesc(
 			"go_build_info",