diff --git a/.github/workflows/test.yml b/.github/workflows/test.yml
index f50a0036..121f549b 100644
--- a/.github/workflows/test.yml
+++ b/.github/workflows/test.yml
@@ -12,8 +12,8 @@ jobs:
       fail-fast: false
       matrix:
         go-version:
-        - '1.18.x'
         - '1.19.x'
+        - '1.20.x'
         os:
         - ubuntu-latest
         - macos-11
@@ -32,7 +32,7 @@ jobs:
         go test -race ./...
 
     - name: Tidy
-      if: matrix.os == 'ubuntu-latest' && matrix.go-version == '1.19.x' # no need to do this everywhere
+      if: matrix.os == 'ubuntu-latest' && matrix.go-version == '1.20.x' # no need to do this everywhere
       run: |
         go mod tidy
 
diff --git a/cmd/testscript/testdata/env_var_with_go.txt b/cmd/testscript/testdata/env_var_with_go.txt
index cf445cac..aa23111e 100644
--- a/cmd/testscript/testdata/env_var_with_go.txt
+++ b/cmd/testscript/testdata/env_var_with_go.txt
@@ -13,8 +13,7 @@ unquote withproxy.txt
 testscript -v noproxy.txt
 stdout ^BANANA=$
 stdout '^GOPATH=\$WORK[/\\]\.gopath'$
-[!go1.13] stdout ^GOPROXY=$
-[go1.13] stdout ^GOPROXY=https://proxy.golang.org,direct$
+stdout ^GOPROXY=https://proxy.golang.org,direct$
 ! stderr .+
 
 env BANANA=banana
@@ -26,8 +25,7 @@ env GOPROXY=
 testscript -v noproxy.txt
 stdout ^BANANA=$
 stdout '^GOPATH=\$WORK[/\\]\.gopath'$
-[!go1.13] stdout ^GOPROXY=$
-[go1.13] stdout ^GOPROXY=https://proxy.golang.org,direct$
+stdout ^GOPROXY=https://proxy.golang.org,direct$
 ! stderr .+
 
 # no GOPROXY, no pass-through, with proxy
diff --git a/fmtsort/mapelem.go b/fmtsort/mapelem.go
index 4e4c2945..98e4e38f 100644
--- a/fmtsort/mapelem.go
+++ b/fmtsort/mapelem.go
@@ -1,6 +1,3 @@
-//go:build go1.12
-// +build go1.12
-
 package fmtsort
 
 import "reflect"
diff --git a/fmtsort/mapelem_1.11.go b/fmtsort/mapelem_1.11.go
deleted file mode 100644
index 873bf7f5..00000000
--- a/fmtsort/mapelem_1.11.go
+++ /dev/null
@@ -1,24 +0,0 @@
-//go:build !go1.12
-// +build !go1.12
-
-package fmtsort
-
-import "reflect"
-
-const brokenNaNs = true
-
-func mapElems(mapValue reflect.Value) ([]reflect.Value, []reflect.Value) {
-	key := mapValue.MapKeys()
-	value := make([]reflect.Value, 0, len(key))
-	for _, k := range key {
-		v := mapValue.MapIndex(k)
-		if !v.IsValid() {
-			// Note: we can't retrieve the value, probably because
-			// the key is NaN, so just do the best we can and
-			// add a zero value of the correct type in that case.
-			v = reflect.Zero(mapValue.Type().Elem())
-		}
-		value = append(value, v)
-	}
-	return key, value
-}
diff --git a/go.mod b/go.mod
index 0a3a9970..1f9a6833 100644
--- a/go.mod
+++ b/go.mod
@@ -1,3 +1,3 @@
 module github.com/rogpeppe/go-internal
 
-go 1.18
+go 1.19
diff --git a/goproxytest/testdata/list.txt b/goproxytest/testdata/list.txt
index 8b05a178..d9b7da9e 100644
--- a/goproxytest/testdata/list.txt
+++ b/goproxytest/testdata/list.txt
@@ -1,6 +1,3 @@
-# prior to go 1.12 you cannot list a module without a requirement
-[!go1.12] go get fruit.com
-
 go list -m -versions fruit.com
 stdout 'v1.0.0 v1.1.0'
 
diff --git a/testscript/exe_go118.go b/testscript/exe_go118.go
index f65a5527..a9bdd810 100644
--- a/testscript/exe_go118.go
+++ b/testscript/exe_go118.go
@@ -1,6 +1,3 @@
-//go:build go1.18
-// +build go1.18
-
 package testscript
 
 import (
diff --git a/testscript/exe_pre_go1.18.go b/testscript/exe_pre_go1.18.go
deleted file mode 100644
index e9323a22..00000000
--- a/testscript/exe_pre_go1.18.go
+++ /dev/null
@@ -1,12 +0,0 @@
-//go:build !go1.18
-// +build !go1.18
-
-package testscript
-
-import (
-	"testing"
-)
-
-func mainStart() *testing.M {
-	return testing.MainStart(nopTestDeps{}, nil, nil, nil)
-}