Switch io_bazel_rules_go to 0.40.0 (#22)

This fixes compilation with more modern versions of Bazel that consider
some rules in io_bazel_rules_go to be broken.

WORKSPACE

@@ -2,18 +2,18 @@ load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 
 http_archive(
     name = "io_bazel_rules_go",
-    sha256 = "099a9fb96a376ccbbb7d291ed4ecbdfd42f6bc822ab77ae6f1b5cb9e914e94fa",
+    sha256 = "bfc5ce70b9d1634ae54f4e7b495657a18a04e0d596785f672d35d5f505ab491a",
     urls = [
-        "https://mirror.bazel.build/github.com/bazelbuild/rules_go/releases/download/v0.35.0/rules_go-v0.35.0.zip",
-        "https://github.com/bazelbuild/rules_go/releases/download/v0.35.0/rules_go-v0.35.0.zip",
+        "https://mirror.bazel.build/github.com/bazelbuild/rules_go/releases/download/v0.40.0/rules_go-v0.40.0.zip",
+        "https://github.com/bazelbuild/rules_go/releases/download/v0.40.0/rules_go-v0.40.0.zip",
     ],
 )
 
 load("@io_bazel_rules_go//go:deps.bzl", "go_register_toolchains", "go_rules_dependencies")
 
 go_rules_dependencies()
 
-go_register_toolchains(version = "1.19.1")
+go_register_toolchains(version = "1.20.5")
 
 PBV = "3.20.3"