ci: Start testing on Go 1.17, drop 1.15 (#4283)

.github/workflows/ci.yml

@@ -19,7 +19,7 @@ jobs:
       fail-fast: false
       matrix:
         os: [ ubuntu-latest, macos-latest, windows-latest ]
-        go: [ '1.15', '1.16' ]
+        go: [ '1.16', '1.17' ]
 
         # Set some variables per OS, usable via ${{ matrix.VAR }}
         # CADDY_BIN_PATH: the path to the compiled Caddy binary, for artifact publishing

.github/workflows/cross-build.yml

@@ -16,7 +16,7 @@ jobs:
       fail-fast: false
       matrix:
         goos: ['android', 'linux', 'solaris', 'illumos', 'dragonfly', 'freebsd', 'openbsd', 'plan9', 'windows', 'darwin', 'netbsd']
-        go: [ '1.15', '1.16' ]
+        go: [ '1.16', '1.17' ]
     runs-on: ubuntu-latest
     continue-on-error: true
     steps:

.github/workflows/release.yml

@@ -11,7 +11,7 @@ jobs:
     strategy:
       matrix:
         os: [ ubuntu-latest ]
-        go: [ '1.16' ]
+        go: [ '1.17' ]
     runs-on: ${{ matrix.os }}
 
     steps: