parse checksum even when no EOL is found

[nixpanic]

In case a checksum file does not end with '\n', the checksum can still
be valid. When hitting EOF, verify that the read line is non-empty, and
continue with parsing.

This addresses kubernetes/minikube#9470.

[hashicorp-cla]

All committers have signed the CLA.

[azr]

Hello there, nice one, this LGTM ! Could you please add a test case for this one as well ?

[nixpanic]

Testcase added, without the change it FAILS:

$ go test . -test.run TestGetFile_checksum_from_file
--- FAIL: TestGetFile_checksum_from_file (0.02s)
    --- FAIL: TestGetFile_checksum_from_file/?checksum=file:http://127.0.0.1:44575/sha512-p-EOF.sum (0.00s)
        get_test.go:444: append: ?checksum=file:http://127.0.0.1:44575/sha512-p-EOF.sum
            
            err: invalid checksum: no checksum found in: http://127.0.0.1:44575/sha512-p-EOF.sum
FAIL
FAIL	github.com/hashicorp/go-getter	0.027s
FAIL

And with the change it passes:

$ go test . -test.run TestGetFile_checksum_from_file
ok  	github.com/hashicorp/go-getter	0.019s

[azr]

Good work, thanks !

[afbjorklund]

Sad that this is needed, but thanks for the workaround! The kubernetes releases still might not verify using other tools though