all: Update Go Module to Go 1.20 (#322)

Reference: #321

.changes/unreleased/NOTES-20230906-055849.yaml

@@ -0,0 +1,8 @@
+kind: NOTES
+body: 'all: This Go module has been updated to Go 1.20 per the [Go support
+  policy](https://go.dev/doc/devel/release#policy). It is recommended to review
+  the [Go 1.20 release notes](https://go.dev/doc/go1.20) before upgrading. Any
+  consumers building on earlier Go versions may experience errors.'
+time: 2023-09-06T05:58:49.879435-04:00
+custom:
+  Issue: "321"

.github/workflows/ci-go.yml

@@ -64,6 +64,7 @@ jobs:
           - '1.2.*'
           - '1.3.*'
           - '1.4.*'
+          - '1.5.*'
   terraform-provider-corner-tfprotov6:
     defaults:
       run:
@@ -101,12 +102,13 @@ jobs:
           - '1.2.*'
           - '1.3.*'
           - '1.4.*'
+          - '1.5.*'
   test:
     name: test (Go v${{ matrix.go-version }})
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go-version: ['1.19', '1.18']
+        go-version: ['1.20', '1.19']
     steps:
       - uses: actions/checkout@c85c95e3d7251135ab7dc9ce3241c5835cc595a9 # v3.5.3
       - uses: actions/setup-go@93397bea11091df50f3d7e59dc26a7711a8bcfbe # v4.1.0

README.md

@@ -33,7 +33,7 @@ is unsupported by the Terraform Plugin SDK team.
 
 This project follows the [support policy](https://golang.org/doc/devel/release.html#policy) of Go as its support policy. The two latest major releases of Go are supported by the project.
 
-Currently, that means Go **1.19** or later must be used when including this project as a dependency.
+Currently, that means Go **1.20** or later must be used when including this project as a dependency.
 
 ## Getting Started
 

go.mod

@@ -1,6 +1,6 @@
 module github.com/hashicorp/terraform-plugin-go
 
-go 1.19
+go 1.20
 
 require (
 	github.com/google/go-cmp v0.5.9

tools/go.mod

@@ -1,6 +1,6 @@
 module tools
 
-go 1.19
+go 1.20
 
 require (
 	github.com/hashicorp/copywrite v0.16.4