I have similar concerns about c# as I do about swift.

I'm less concerned about go, because unlike swift and c# it was designed from the beginning to be cross-platform and if anything Linux is the best supported OS. But barely so. Also, if Google were to discontinue support, or change the license, or do something else disruptive, I have more faith that the ecosystem would create a fork to continue the language.

FWIW, my biggest concern isn't that the language would be completely abandoned, it is that the company would diminish or drop support for tooling on OSes and editors and IDEs that compete with the company's products (Mac OS and Xcode for apple, Windows and Visual Studio for MS).

Microsoft’s market position is reliant on Linux and access to Linux development to keep Azure competitive. Cross-platform capabilities on the .Net VM are critical to compete with the JVM and associated databases. C# has been windows-first for a while, but the core cross-platform capabilities are not going to disappear, the tooling is all CLI based/capable now, the entanglements tend to be platform and service based.

That said, F# was years ahead of C# in features C# is still chasing, and is driven mostly by the open source community. That community is more in academic and finance areas where Linux-first is common. The language is standardized and plugged into VM improvements over time.

Frankly, I see the lesser degree of entanglement with MS corporate interests as a boon for the language and its ecosystems long-term utility.