cmd/bench: go fmt

Change-Id: I8b846ce7976429a51f45117cea13a06d6ac28ba7
Reviewed-on: https://go-review.googlesource.com/c/benchmarks/+/377274
Trust: Michael Pratt <mpratt@google.com>
Run-TryBot: Michael Pratt <mpratt@google.com>
Reviewed-by: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
diff --git a/cmd/bench/gotest.go b/cmd/bench/gotest.go
index accf6a0..a98ce20 100644
--- a/cmd/bench/gotest.go
+++ b/cmd/bench/gotest.go
@@ -26,7 +26,7 @@
 		}
 	}
 	if needGOROOT {
-		env = append(env, "GOROOT=" + goroot)
+		env = append(env, "GOROOT="+goroot)
 	}
 	cmd.Env = env