Why doesn't `go env` command reflect change in environment variable?

In my system, GOBIN variable was unset (empty value). Now unlike some other GO env variables, this seems unset even in the output for go env command. (I'm user ubuntu, so ~ is /home/ubuntu/)

echo $GOBIN
   //empty
echo $GOPATH
   //empty
echo $GOROOT
   //empty
go env GOBIN
   //empty
go env GOPATH
/home/ubuntu/go
go env GOROOT
/usr/local/go
which go
/usr/local/go/bin/go

1. Why does go env give values different from the system environment variables? I couldn't find any documentation on this, but my assumption is that if env variables are not set at the system level, Golang sets default values - which are shown by go env. Is this assumption correct?

2. Why is GOBIN unset? I tried setting the system env variable explicitly, but it doesn't get reflected in go env, even though the system env variable seems to get modified. Why is that so?

echo $GOBIN
     //empty
go env GOBIN
     //empty
go env GOPATH
/home/ubuntu/go
GOBIN=‘/home/ubuntu/go/bin’
echo $GOBIN
/home/ubuntu/go/bin
go env GOBIN
     //empty

The official documentation (https://pkg.go.dev/cmd/go) says:
> Env prints Go environment information

but it doesn't mention where the said variables are sourced from.

Problem X (https://xyproblem.info/)

I am trying to install Delve (https://github.com/go-delve/delve), and my system has two go versions (go1.10.1 and go1.17.8), and I plan to use the latter (unfortunately can't remove the former)

go1.17.8 go install github.com/go-delve/delve/cmd/dlv@latest makes a new directory at /home/ubuntu => go and adds Delve here. But dlv version is unrecognized.
From go help env, GOBIN is where go install should install binaries - in my case it's unset, so I'm guessing Golang installs it at GOPATH. But even then, I expected the binary to be recognized. I also tried adding the location to my PATH, but that didn't work either.

3. Should I set my GOBIN to anything specific before installation via go1.17.8?
4. Is my system having 2 go versions (which go is pointing to the go1.10.1 version), causing this? (1.10.1 doesn't have Modules support, but I was trying the install via go.17.8, so I assumed this wouldn't be an issue)

go on Linux will store persistent settings to this file:

$HOME/.config/go/env

via the go env -w command. Since the go tool loads settings from both this config and ENV VARS - this explains why you may see differing values. The go tool combines both.

These go env variables are variables set at the time of installation your binary.

Please refer the code of https://github.com/golang:

• as per https://github.com/golang/go/blob/master/src/internal/buildcfg/cfg.go,
  these variables are either taken from environment variables or default variables.

• These default values are generated as per runtime https://github.com/golang/go/blob/master/src/cmd/dist/buildruntime.go#L48

Thus, these variables do not appear as part of Operating systems environment variables.

These variables can be overridden by config file at os.UserConfigDir or by command go env NAME=VALUE.