If the problem is that you are not seeing your changes to the file take effect, just open a new terminal window, and it will be "sourced". You will be able to use the proper PATH etc with each subsequent terminal window.
No need to start, it would automatically executed while you startup your mac terminal / bash. Whenever you do a change, you may need to restart the terminal.
~ is the default path for .bash_profile
On MacOS: add source ~/.bash_profile to the end of ~/.zshrc.
Then this profile will be in effect when you open zsh.
If you change .bash_profile, it only applies to new Terminal sessions.
To apply it to an existing session, run source ~/.bash_profile. You can run any Bash script this way - think of executing source as the same as typing commands in the Terminal window (from the specified script).
More info: How to reload .bash_profile from the command line?
Bonus: You can make environment variables available to OSX applications - not just the current Bash session but apps like Visual Studio Code or IntelliJ - using launchctl setenv GOPATH "${GOPATH:-}"
As @kojiro said, you don't want to "run" this file. Source it as he says. It should get "sourced" at startup. Sourcing just means running every line in the file, including the one you want to get run. If you want to make sure a folder is in a certain path environment variable (as it seems you want from one of your comments on another solution), execute
$ echo $PATH
At the command line. If you want to check that your ~/.bash_profile is being sourced, either at startup as it should be, or when you source it manually, enter the following line into your ~/.bash_profile file:
$ echo "Hello I'm running stuff in the ~/.bash_profile!"
You would never want to run that, but you may want to source it.
. ~/.bash_profile
source ~/.bash_profile
both should work. But this is an odd request, because that file should be sourced automatically when you start bash, unless you're explicitly starting it non-interactively. From the man page:
When bash is invoked as an interactive login shell, or as a non-interactive shell with the --login option, it first reads and executes commands from the file /etc/profile, if that file exists. After reading that file, it looks for ~/.bash_profile, ~/.bash_login, and ~/.profile, in that order, and reads and executes commands from the first one that exists and is readable. The --noprofile option may be used when the shell is started to inhibit this behavior.
Source: Stackoverflow.com