Implement N-1 support policy for Go versions

Makefile

@@ -166,6 +166,8 @@ lint:
 	@[ ! -s "$(FMT_LOG)" -a ! -s "$(IMPORT_LOG)" ] || (echo "License check or import ordering failures, run 'make fmt'" | cat - $(FMT_LOG) $(IMPORT_LOG) && false)
 	./scripts/check-semconv-version.sh
 
+	./scripts/check-go-version.sh
+
 .PHONY: build-examples
 build-examples:
 	$(GOBUILD) -o ./examples/hotrod/hotrod-$(GOOS)-$(GOARCH) ./examples/hotrod/main.go

README.md

@@ -141,6 +141,16 @@ For example, consider a scenario where v1.28.0 is released on 01-Jun-2021 contai
 This flag will remain in a deprecated state until the later of 01-Sep-2021 or v1.30.0 where it _can_ be removed on or after either of those events.
 It may remain deprecated for longer than the aforementioned grace period.
 
+## Go Version Compatibility Guarantees
+
+The Jaeger project attempts to track the currently supported versions of Go, as [defined by the Go team](https://go.dev/doc/devel/release#policy).
+Removing support for an unsupported Go version is not considered a breaking change.
+
+Starting with the release of Go 1.21, support for Go versions will be updated as follows:
+
+1. Soon after the release of a new Go minor version `N`, updates will be made to the build and tests steps to accommodate the latest Go minor version.
+2. Soon after the release of a new Go minor version `N`, support for Go version `N-2` will be removed and version `N-1` will become the minimum required version.
+
 ## Related Repositories
 
 ### Documentation

scripts/check-go-version.sh

@@ -0,0 +1,91 @@
+#!/bin/bash
+
+version_regex='[0-9]\.[0-9][0-9]'
+update=false
+verbose=false
+
+while getopts "uvd" opt; do
+    case $opt in
+        u) update=true ;;
+        v) verbose=true ;;
+        x) set -x ;;
+        *) echo "Usage: $0 [-u] [-v] [-d]" >&2
+           exit 1
+           ;;
+    esac
+done
+
+# Fetch latest go release version
+go_latest_version=$(curl -s https://go.dev/dl/?mode=json | jq -r '.[0].version' | awk -F'.' '{gsub("go", ""); print $1"."$2}')
+go_previous_version="${go_latest_version%.*}.$((10#${go_latest_version#*.} - 1))"
+
+files_to_update=0
+
+function update() {
+    local file=$1
+    local pattern=$2
+    local current=$3
+    local target=$4
+
+    newfile=$(mktemp)
+    old_IFS=$IFS
+    IFS=''
+    while read -r line; do
+        match=$(echo $line | grep -e "$pattern")
+        if [[ "$match" != "" ]]; then
+            line=$(echo "$line" | sed "s/${current}/${target}/g")
+        fi
+        echo $line >> $newfile
+    done < $file
+    IFS=$old_IFS
+
+    if [ $verbose = true ]; then
+        diff $file $newfile
+    fi
+
+    mv $newfile $file
+}
+
+function check() {
+    local file=$1
+    local pattern=$2
+    local target=$3
+
+    go_version=$(grep -e "$pattern" $file | head -1 | sed "s/^.*\($version_regex\).*$/\1/")
+
+    if [ "$go_version" = "$target" ]; then
+        mismatch=''
+    else
+        mismatch='*** needs update ***'
+        files_to_update=$((files_to_update+1))
+    fi
+
+    if [[ $update = true && "$mismatch" != "" ]]; then
+        update "$file" "$pattern" "$go_version" "$target"
+        mismatch="*** => $target ***"
+    fi
+
+    printf "%-50s Go version: %s %s\n" "$file" "$go_version" "$mismatch"
+}
+
+check go.mod "^go\s\+$version_regex" $go_previous_version
+
+check docker/Makefile "^.*golang:$version_regex" $go_latest_version
+
+gha_workflows=$(grep -rl go-version .github)
+for gha_workflow in ${gha_workflows[@]}; do
+    check $gha_workflow "^\s*go-version:\s\+$version_regex" $go_latest_version
+done
+
+check .golangci.yml "go:\s\+\"$version_regex\"" $go_previous_version
+
+if [ $files_to_update -eq 0 ]; then
+    echo "All files are up to date."
+else
+    if [[ $update = true ]]; then
+        echo "$files_to_update file(s) updated."
+    else
+        echo "$files_to_update file(s) must be updated. Rerun this script with -u argument."
+        exit 1
+    fi
+fi