Flaky warning when running tests

[invidian]

It seems that running tests sometimes produce a warning, which I guess could be fixed.

0 ✓ (28.1ms) 12:26:07 invidian@dellxps15mateusz ~/repos/kinvolk/go-shamir (pr/2)$ make
go build -o bin/shamir cli/main.go
./tests/shamir
OK
0 ✓ (255ms) 12:26:08 invidian@dellxps15mateusz ~/repos/kinvolk/go-shamir (pr/2)$ make test
go build -o bin/shamir cli/main.go
./tests/shamir
./tests/shamir: line 14: warning: command substitution: ignored null byte in input
OK
0 ✓ (244ms) 12:26:11 invidian@dellxps15mateusz ~/repos/kinvolk/go-shamir (pr/2)$ make test
go build -o bin/shamir cli/main.go
./tests/shamir
OK
0 ✓ (262ms) 12:26:20 invidian@dellxps15mateusz ~/repos/kinvolk/go-shamir (pr/2)$ make test
go build -o bin/shamir cli/main.go
./tests/shamir
OK
0 ✓ (264ms) 12:26:21 invidian@dellxps15mateusz ~/repos/kinvolk/go-shamir (pr/2)$ make test
go build -o bin/shamir cli/main.go
./tests/shamir
OK
0 ✓ (217ms) 12:26:22 invidian@dellxps15mateusz ~/repos/kinvolk/go-shamir (pr/2)$ make test
go build -o bin/shamir cli/main.go
./tests/shamir
OK
0 ✓ (302ms) 12:26:22 invidian@dellxps15mateusz ~/repos/kinvolk/go-shamir (pr/2)$ make test
go build -o bin/shamir cli/main.go
./tests/shamir
OK
0 ✓ (289ms) 12:26:23 invidian@dellxps15mateusz ~/repos/kinvolk/go-shamir (pr/2)$ make test
go build -o bin/shamir cli/main.go
./tests/shamir
OK
0 ✓ (249ms) 12:26:23 invidian@dellxps15mateusz ~/repos/kinvolk/go-shamir (pr/2)$ make test
go build -o bin/shamir cli/main.go
./tests/shamir
./tests/shamir: line 15: warning: command substitution: ignored null byte in input
OK

[vbatts]

still the case. Not sure of the fix.