The error message is error building application: exec: "C:\\Program Files\\Go\\bin": file does not exist, and I got it by running fyne install (or fyne serve or fyne package).
I suspect that it has something to do with my GOPATH, but not sure what.
Some environment variables:
GOPATH is a user variable : C:\Users\ethan\go\bin
go is a system variable: C:\Program Files\Go\bin
Both of those are also in the Path system variable, as well as the directory of the run.go file in the working directory and its parent.
C:\Program Files\Go\bin
Contains files:
go.exe
gofmt.exe
C:\Users\ethan\go\bin
Contains files:
fyne.exe
gopls.exe
fyne-cross.exe
staticcheck.exe
dlv.exe
yaegi.exe
gopls.exe--