Revert "update CI and everything to Go 1.14."

This reverts commit 905fe9f6a2.

We're not quite ready to update the Mac/iOS builds to 1.14.

.github/workflows/cross-darwin.yml

@@ -16,10 +16,10 @@ jobs:
 
     steps:
 
-    - name: Set up Go 1.14
+    - name: Set up Go 1.13
       uses: actions/setup-go@v1
       with:
-        go-version: 1.14
+        go-version: 1.13
       id: go
 
     - name: Check out code into the Go module directory

.github/workflows/cross-freebsd.yml

@@ -16,10 +16,10 @@ jobs:
 
     steps:
 
-    - name: Set up Go 1.14
+    - name: Set up Go 1.13
       uses: actions/setup-go@v1
       with:
-        go-version: 1.14
+        go-version: 1.13
       id: go
 
     - name: Check out code into the Go module directory

.github/workflows/cross-openbsd.yml

@@ -16,10 +16,10 @@ jobs:
 
     steps:
 
-    - name: Set up Go 1.14
+    - name: Set up Go 1.13
       uses: actions/setup-go@v1
       with:
-        go-version: 1.14
+        go-version: 1.13
       id: go
 
     - name: Check out code into the Go module directory

.github/workflows/cross-windows.yml

@@ -16,10 +16,10 @@ jobs:
 
     steps:
 
-    - name: Set up Go 1.14
+    - name: Set up Go 1.13
       uses: actions/setup-go@v1
       with:
-        go-version: 1.14
+        go-version: 1.13
       id: go
 
     - name: Check out code into the Go module directory

.github/workflows/linux.yml

@@ -16,10 +16,10 @@ jobs:
 
     steps:
 
-    - name: Set up Go 1.14
+    - name: Set up Go 1.13
       uses: actions/setup-go@v1
       with:
-        go-version: 1.14
+        go-version: 1.13
       id: go
 
     - name: Check out code into the Go module directory

.github/workflows/staticcheck.yml

@@ -13,10 +13,10 @@ jobs:
     runs-on: ubuntu-latest
 
     steps:
-    - name: Set up Go 1.14
+    - name: Set up Go 1.13
       uses: actions/setup-go@v1
       with:
-        go-version: 1.14
+        go-version: 1.13
 
     - name: Check out code
       uses: actions/checkout@v1