XO1503: the Go backend finds no go command

The Go backend (the default for xo build, xo run, and xo test) writes Go source and compiles it with the go command: $XO_GO, else go on PATH. When $XO_GO is not an executable file, or PATH has no go, the build stops before generating code with this diagnostic instead of failing inside the go build. The native backends (arm64, LLVM) do not run Go and build without it. See decision 0176.

Example

$ xo run .
XO1503: the Go backend runs the go command, but there is no go on PATH; install Go 1.24 or newer (https://go.dev/dl), set XO_GO to its go command, or build with --backend=arm64 or llvm, which need no Go

Fix

# install Go 1.24 or newer from https://go.dev/dl, or point Xo at one:
XO_GO=$HOME/sdk/go1.26.1/bin/go xo run .
# or use a native backend, which does not run Go:
xo run --backend=arm64 .

Run xo explain XO1503 for this text in a terminal, or see section 10.6 of the specification.