go.mod: bump to go1.16

Signed-off-by: Evgenii Stratonikov <evgeniy@nspcc.ru>

.github/workflows/run_tests.yml

@@ -33,7 +33,7 @@ jobs:
       - name: Set up Go
         uses: actions/setup-go@v2
         with:
-          go-version: 1.17
+          go-version: 1.18
 
       - name: Restore Go modules from cache
         uses: actions/cache@v2
@@ -60,14 +60,14 @@ jobs:
     strategy:
       matrix:
         os: [ ubuntu-20.04, windows-2022 ]
-        go_versions: [ '1.15', '1.16', '1.17' ]
+        go_versions: [ '1.16', '1.17', '1.18' ]
         exclude:
-          - os: windows-2022
-            go_versions: '1.15'
           - os: windows-2022
             go_versions: '1.16'
-          - os: ubuntu-20.04
+          - os: windows-2022
             go_versions: '1.17'
+          - os: ubuntu-20.04
+            go_versions: '1.18'
       fail-fast: false
     steps:
       - uses: actions/checkout@v2

go.mod

@@ -1,6 +1,6 @@
 module github.com/nspcc-dev/tzhash
 
-go 1.12
+go 1.16
 
 require (
 	github.com/davecgh/go-spew v1.1.1 // indirect