Fix main startup (#232)

Set version and name of the program. And then call coremain.Run().

The coremain split makes CoreDNS embeddable.

Also see #189 for an old PR.

coremain/run_test.go

@@ -0,0 +1,44 @@
+package coremain
+
+import (
+	"runtime"
+	"testing"
+)
+
+func TestSetCPU(t *testing.T) {
+	currentCPU := runtime.GOMAXPROCS(-1)
+	maxCPU := runtime.NumCPU()
+	halfCPU := int(0.5 * float32(maxCPU))
+	if halfCPU < 1 {
+		halfCPU = 1
+	}
+	for i, test := range []struct {
+		input     string
+		output    int
+		shouldErr bool
+	}{
+		{"1", 1, false},
+		{"-1", currentCPU, true},
+		{"0", currentCPU, true},
+		{"100%", maxCPU, false},
+		{"50%", halfCPU, false},
+		{"110%", currentCPU, true},
+		{"-10%", currentCPU, true},
+		{"invalid input", currentCPU, true},
+		{"invalid input%", currentCPU, true},
+		{"9999", maxCPU, false}, // over available CPU
+	} {
+		err := setCPU(test.input)
+		if test.shouldErr && err == nil {
+			t.Errorf("Test %d: Expected error, but there wasn't any", i)
+		}
+		if !test.shouldErr && err != nil {
+			t.Errorf("Test %d: Expected no error, but there was one: %v", i, err)
+		}
+		if actual, expected := runtime.GOMAXPROCS(-1), test.output; actual != expected {
+			t.Errorf("Test %d: GOMAXPROCS was %d but expected %d", i, actual, expected)
+		}
+		// teardown
+		runtime.GOMAXPROCS(currentCPU)
+	}
+}