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 <[email protected]>

Author: beorn7

.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

@@ -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",