These are good points. what would change your mind besides the long term? What if you for example were in a team with multiple devs working on the backend?
And what do you consider long-term? :)
To answer your question properly: I think programming language should be a financial choice for any company, and one of the highest cost factors is developer hours. All that i've described earlier is about optimising for developer hours.
If there's a nieche reason to prefer a language that may override all points i've described. For example, hardware support, availability of project-specific library, language preferences of customers, compliance requirements.
As for long term, i'd say 3-5 years is a tipping point, where maintaining PHP/Python becames more painful then just using Go. Probably a bit sooner for nodejs with the npm dependency hell. But i'd warn you about choosing Go due to planning your product to exist for more than 3-5 years. You'll almost certainly have multiple rewrites of your code before you get to a state where it actually lives for 5 years - if at all. Do yourself a favor and prototype in a quick language. Maybe even have your first versions out ugly and bodged. You'll have a chance to rewrite if and when you have customers and a working business model.
Lastly but most importantly, these are commercial considerations. For a non-commercial project, you should ignore these and optimize for developer-happiness instead. I like Go. I'd choose Go over PHP/Python/nodejs anytime as a developer. You should choose whatever you like the best. If you ask me, you should like Go the best :-)