all: Bump Go Version to 1.18 (#1027)

Reference: #834
Reference: #1026
Reference: hashicorp/terraform-website#2279

Updates everything for Go 1.18 by running the following:

```shell
go mod edit -go=1.18
go mod tidy
go fix ./...
```

And updating textual files such as GitHub Actions workflows and the README.

Author: bflad

.changelog/1027.txt

@@ -0,0 +1,3 @@
+```release-note:note
+This Go module has been updated to Go 1.18 per the [Go support policy](https://golang.org/doc/devel/release.html#policy). Any consumers building on earlier Go versions may experience errors.
+```

.github/workflows/ci-go.yml

@@ -48,7 +48,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        go-version: [ '1.18', '1.17' ]
+        go-version: [ '1.19', '1.18' ]
     steps:
       - uses: actions/checkout@v3
       - uses: actions/setup-go@v3

README.md

@@ -18,7 +18,7 @@ When running provider tests, Terraform 0.12.26 or later is needed for version 2.
 
 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 **1.17** or later must be used when including this project as a dependency.
+Currently, that means Go **1.18** 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-sdk/v2
 
-go 1.17
+go 1.18
 
 require (
 	github.com/apparentlymart/go-cidr v1.1.0

go.sum

@@ -18,6 +18,8 @@ import (
 	"github.com/hashicorp/terraform-plugin-sdk/v2/terraform"
 )
 
+const invalidDurationErrMsg = "time: invalid duration \"invalid\""
+
 func TestProviderGetSchema(t *testing.T) {
 	// This functionality is already broadly tested in core_schema_test.go,
 	// so this is just to ensure that the call passes through correctly.

helper/schema/provider_go115_test.go

@@ -136,7 +136,7 @@ Create a [GitHub Actions workflow](https://docs.github.com/en/actions/using-work
 
 Use the [`matrix`](https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idstrategymatrix) strategy for more advanced configuration, such as running acceptance testing against multiple Terraform CLI versions.
 
-The following example workflow runs acceptance testing for the provider using the latest patch versions of Go 1.17 and Terraform CLI 1.1:
+The following example workflow runs acceptance testing for the provider using the latest patch versions of Go 1.18 and Terraform CLI 1.2:
 
 ```yaml
 name: Terraform Provider Tests
@@ -156,13 +156,13 @@ jobs:
     name: Acceptance Tests
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions/setup-go@v2
+      - uses: actions/checkout@v3
+      - uses: actions/setup-go@v3
         with:
-          go-version: '1.17'
-      - uses: hashicorp/setup-terraform@v1
+          go-version: '1.18'
+      - uses: hashicorp/setup-terraform@v2
         with:
-          terraform_version: '1.1.*'
+          terraform_version: '1.2.*'
           terraform_wrapper: false
       - run: go test -v -cover ./...
         env:
@@ -171,15 +171,15 @@ jobs:
     name: Unit Tests
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions/setup-go@v2
+      - uses: actions/checkout@v3
+      - uses: actions/setup-go@v3
         with:
-          go-version: '1.17'
+          go-version: '1.18'
       - run: go test -v -cover ./...
 ```
 
 
-The following example workflow runs acceptance testing for the provider using the latest patch versions of Go 1.17 and Terraform CLI 0.12 through 1.1:
+The following example workflow runs acceptance testing for the provider using the latest patch versions of Go 1.18 and Terraform CLI 0.12 through 1.2:
 
 ```yaml
 name: Terraform Provider Tests
@@ -208,12 +208,13 @@ jobs:
           - '0.15.*'
           - '1.0.*'
           - '1.1.*'
+          - '1.2.*'
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions/setup-go@v2
+      - uses: actions/checkout@v3
+      - uses: actions/setup-go@v3
         with:
-          go-version: '1.17'
-      - uses: hashicorp/setup-terraform@v1
+          go-version: '1.18'
+      - uses: hashicorp/setup-terraform@v2
         with:
           terraform_version: ${{ matrix.terraform-version }}
           terraform_wrapper: false
@@ -224,10 +225,10 @@ jobs:
     name: Unit Tests
     runs-on: ubuntu-latest
     steps:
-      - uses: actions/checkout@v2
-      - uses: actions/setup-go@v2
+      - uses: actions/checkout@v3
+      - uses: actions/setup-go@v3
         with:
-          go-version: '1.17'
+          go-version: '1.18'
       - run: go test -v -cover ./...
 ```