Update minimum supported version to go1.11 (#281)

.github/workflows/test.yml

diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index 6b1b1c4..2e6a1c9 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -9,7 +9,7 @@
         working-directory: ${{ env.GOPATH }}/src/github.com/${{ github.repository }}
     strategy:
       matrix:
-        go-version: [1.8.x, 1.9.x, 1.10.x, 1.11.x, 1.12.x, 1.13.x, 1.14.x, 1.15.x, 1.16.x]
+        go-version: [1.11.x, 1.12.x, 1.13.x, 1.14.x, 1.15.x, 1.16.x, 1.17.x]
         os: [ubuntu-latest, macos-latest]
     runs-on: ${{ matrix.os }}
     steps:

go.mod

diff --git a/go.mod b/go.mod
index 5391dee..4cdb762 100644
--- a/go.mod
+++ b/go.mod
@@ -1,5 +1,5 @@
 module github.com/google/go-cmp
 
-go 1.8
+go 1.11
 
 require golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543