Go 文件编译失败 - 在此代码块中重新声明 "xxxx"

在尝试编译 Go 文件时，作者遇到了错误，提示变量在当前代码块中被重新声明。该错误与同时安装了多个 Go 版本有关。重新安装 Go 并将环境变量 GOPATH 和 GOROOT 设置为适当的值解决了问题。

我是 go 新手，我按照网站和 youtube 视频中的说明进行操作，当我运行 go build hello.go 时，出现以下错误：

go: disabling cache (/home/myuser/.cache/go-build) due to initialization failure: open /home/myuser/.cache/go-build/log.txt: permission denied
# runtime
/usr/local/go/src/runtime/map.go:64:2: bucketCntBits redeclared in this block
    previous declaration at /usr/local/go/src/runtime/hashmap.go:64:18
/usr/local/go/src/runtime/map.go:65:2: bucketCnt redeclared in this block
    previous declaration at /usr/local/go/src/runtime/hashmap.go:65:23
/usr/local/go/src/runtime/map.go:69:2: loadFactorNum redeclared in this block
    previous declaration at /usr/local/go/src/runtime/hashmap.go:69:18
/usr/local/go/src/runtime/map.go:70:2: loadFactorDen redeclared in this block
    previous declaration at /usr/local/go/src/runtime/hashmap.go:70:18
/usr/local/go/src/runtime/map.go:76:2: maxKeySize redeclared in this block
    previous declaration at /usr/local/go/src/runtime/hashmap.go:76:17
/usr/local/go/src/runtime/map.go:77:2: maxValueSize redeclared in this block
    previous declaration at /usr/local/go/src/runtime/hashmap.go:77:17
/usr/local/go/src/runtime/map.go:82:2: dataOffset redeclared in this block
    previous declaration at /usr/local/go/src/runtime/hashmap.go:85:4
/usr/local/go/src/runtime/map.go:91:2: empty redeclared in this block
    previous declaration at /usr/local/go/src/runtime/hashmap.go:91:19
/usr/local/go/src/runtime/map.go:92:2: evacuatedEmpty redeclared in this block
    previous declaration at /usr/local/go/src/runtime/hashmap.go:92:19
/usr/local/go/src/runtime/map.go:93:2: evacuatedX redeclared in this block
    previous declaration at /usr/local/go/src/runtime/hashmap.go:93:19
/usr/local/go/src/runtime/map.go:93:2: too many errors

它写了 permission returned 但我尝试使用 sudo go build 运行它，但它也失败了：

sudo: go: 找不到命令

我正在使用 ubuntu 16.4。 我的 go 文件 hello.go 位于 $home/desktop/go/src/hello 中。

我的文件 $home/myuser/.profile 包含：

path="$home/bin:$home/.local/bin:$path:/usr/local/go/bin"

解决方案

重新安装 go 解决了问题。
发生这个问题是因为我在旧版本之上安装了新版本的 go。

解决方案：
1. Remove Go：rm -rvf /usr/local/go/
2.从Golang website重新安装：

cd ~/go/downloads
// depends on the version you download
tar -c /usr/local -xzf go1.14.4.linux-amd64.tar.gz
export path=$path:/usr/local/go/bin
cd ~/go/src/myproj/
go build
// no errors

gopath

the gopath environment variable lists places to look for go code.
on unix, the value is a colon-separated string. on windows, the value 
is a semicolon-separated string. on plan 9, the value is a list.

gopath must be set to get, build and install packages outside the standard go tree.
use tool like dep to segregate your different go project, maintaining your project dependencies.

goroot

The Go binary distributions assume they will be installed in /usr/local/go (or c:\Go under Windows), but it is possible to install 
the Go tools to a different location. In this case you must set the 
GOROOT environment variable to point to the directory in which it was installed.

所以它总是首选创建自己的 gopath 来编译代码。 gopath 适用于您自己的 go 项目/第 3 方库（使用“go get”下载）。

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