go install時にis not in stdエラー

単純なミスに気が付かずにハマったので備忘録。
検証のためにGoのインストールやアンインストールを繰り返していたら下記エラーが出るようになった。

```zsh
$ go install golang.org/dl/go1.21.0@latest
../../go/pkg/mod/golang.org/dl@v0.0.0-20231219203010-00f4782d5d4c/internal/version/version.go:9:2: package archive/tar is not in std (/opt/homebrew/Cellar/go/1.21.5/src/archive/tar)
../../go/pkg/mod/golang.org/dl@v0.0.0-20231219203010-00f4782d5d4c/internal/version/version.go:10:2: package archive/zip is not in std (/opt/homebrew/Cellar/go/1.21.5/src/archive/zip)
../../go/pkg/mod/golang.org/dl@v0.0.0-20231219203010-00f4782d5d4c/internal/version/version.go:11:2: package compress/gzip is not in std (/opt/homebrew/Cellar/go/1.21.5/src/compress/gzip)
../../go/pkg/mod/golang.org/dl@v0.0.0-20231219203010-00f4782d5d4c/internal/version/version.go:12:2: package crypto/sha256 is not in std (/opt/homebrew/Cellar/go/1.21.5/src/crypto/sha256)
../../go/pkg/mod/golang.org/dl@v0.0.0-20231219203010-00f4782d5d4c/internal/version/version.go:13:2: package errors is not in std (/opt/homebrew/Cellar/go/1.21.5/src/errors)
../../go/pkg/mod/golang.org/dl@v0.0.0-20231219203010-00f4782d5d4c/internal/version/gotip.go:8:2: package fmt is not in std (/opt/homebrew/Cellar/go/1.21.5/src/fmt)
../../go/pkg/mod/golang.org/dl@v0.0.0-20231219203010-00f4782d5d4c/internal/version/version.go:15:2: package io is not in std (/opt/homebrew/Cellar/go/1.21.5/src/io)
../../go/pkg/mod/golang.org/dl@v0.0.0-20231219203010-00f4782d5d4c/internal/version/gotip.go:9:2: package log is not in std (/opt/homebrew/Cellar/go/1.21.5/src/log)
../../go/pkg/mod/golang.org/dl@v0.0.0-20231219203010-00f4782d5d4c/internal/version/version.go:17:2: package net/http is not in std (/opt/homebrew/Cellar/go/1.21.5/src/net/http)
../../go/pkg/mod/golang.org/dl@v0.0.0-20231219203010-00f4782d5d4c/internal/version/gotip.go:10:2: package os is not in std (/opt/homebrew/Cellar/go/1.21.5/src/os)
../../go/pkg/mod/golang.org/dl@v0.0.0-20231219203010-00f4782d5d4c/internal/version/gotip.go:11:2: package os/exec is not in std (/opt/homebrew/Cellar/go/1.21.5/src/os/exec)
../../go/pkg/mod/golang.org/dl@v0.0.0-20231219203010-00f4782d5d4c/internal/version/version.go:20:2: package os/signal is not in std (/opt/homebrew/Cellar/go/1.21.5/src/os/signal)
../../go/pkg/mod/golang.org/dl@v0.0.0-20231219203010-00f4782d5d4c/internal/version/version.go:21:2: package os/user is not in std (/opt/homebrew/Cellar/go/1.21.5/src/os/user)
../../go/pkg/mod/golang.org/dl@v0.0.0-20231219203010-00f4782d5d4c/internal/version/version.go:22:2: package path is not in std (/opt/homebrew/Cellar/go/1.21.5/src/path)
../../go/pkg/mod/golang.org/dl@v0.0.0-20231219203010-00f4782d5d4c/internal/version/gotip.go:12:2: package path/filepath is not in std (/opt/homebrew/Cellar/go/1.21.5/src/path/filepath)
../../go/pkg/mod/golang.org/dl@v0.0.0-20231219203010-00f4782d5d4c/internal/version/gotip.go:13:2: package regexp is not in std (/opt/homebrew/Cellar/go/1.21.5/src/regexp)
../../go/pkg/mod/golang.org/dl@v0.0.0-20231219203010-00f4782d5d4c/internal/version/gotip.go:14:2: package runtime is not in std (/opt/homebrew/Cellar/go/1.21.5/src/runtime)
../../go/pkg/mod/golang.org/dl@v0.0.0-20231219203010-00f4782d5d4c/internal/version/gotip.go:15:2: package strconv is not in std (/opt/homebrew/Cellar/go/1.21.5/src/strconv)
../../go/pkg/mod/golang.org/dl@v0.0.0-20231219203010-00f4782d5d4c/internal/version/version.go:26:2: package strings is not in std (/opt/homebrew/Cellar/go/1.21.5/src/strings)
../../go/pkg/mod/golang.org/dl@v0.0.0-20231219203010-00f4782d5d4c/internal/version/signal_unix.go:11:2: package syscall is not in std (/opt/homebrew/Cellar/go/1.21.5/src/syscall)
../../go/pkg/mod/golang.org/dl@v0.0.0-20231219203010-00f4782d5d4c/internal/version/version.go:27:2: package time is not in std (/opt/homebrew/Cellar/go/1.21.5/src/time)
```

Goのインストール方法を変えたり、キャッシュを消したりなど色々と試したが、
結局のところ、Goの切替時に、GOROOTの設定に誤ってGOPATHを設定していた。

```
$ go env GOROOT
/Users/mitsuaki.ihara/go
```

下記で解消。
※下記コマンドはHomebrewでインストールしたGoの場合

```zsh
$ go env -w GOROOT=$(brew --prefix golang)/libexec
```

再実行。

```zsh
$ go install golang.org/dl/go1.21.0@latest
```

## 参考

* [go installがうまくいかない](https://scrapbox.io/shinobe179-public/go_install%E3%81%8C%E3%81%86%E3%81%BE%E3%81%8F%E3%81%84%E3%81%8B%E3%81%AA%E3%81%84)