ng/eval: possible race triggered by eval/testdata/method{1,2}

[sbinet]

with go1.10beta1, running the following failed:

$> go test -v -count=3 ./eval
=== RUN   TestExprs
--- PASS: TestExprs (0.00s)
[...]
    --- FAIL: TestPrograms/method1 (0.00s)
    	eval_test.go:212: 25: ng eval panic: no method pool entries available for Read, func([]uint8) (int, error)
    --- FAIL: TestPrograms/method2 (0.00s)
    	eval_test.go:212: 13: ng eval panic: no method pool entries available for Read, func([]uint8) (int, error)
[...]

[crawshaw]

I am actively working on this. The method pool is a failed experiment that needs to go. I just keep getting distracted by yaks to shave when I try to fix this.

My intention is to use the Go-generating backend to construct method types usable that can be loaded as plugins when a methodik is defined. The one issue is how to use named types as part of the type (or method parameters). Restricting methodiks to struct types solves the former, but the latter is tricky.