added Go variant

- using homegrown approval test function

go/theatre/testdata/.gitignore

@@ -0,0 +1 @@
+*.out.*

go/theatre/testdata/TestPrinterPrintByApproval/1.approved.txt

@@ -0,0 +1,6 @@
+Statement for BigCo
+  Hamlet: $650.00 (55 seats)
+  As You Like It: $580.00 (35 seats)
+  Othello: $500.00 (40 seats)
+Amount owed is $1,730.00
+You earned 47 credits

go/theatre/testdata/TestPrinterPrintByApproval/1.in.json

@@ -0,0 +1,15 @@
+{
+  "plays": [
+    { "id": "hamlet", "play": { "name": "Hamlet", "type": "tragedy" } },
+    { "id": "as-like", "play": { "name": "As You Like It", "type": "comedy" } },
+    { "id": "othello", "play": { "name": "Othello", "type": "tragedy" } }
+    ],
+  "invoice": {
+    "customer": "BigCo",
+    "performances": [
+      {"playId": "hamlet", "audience": 55 },
+      {"playId": "as-like", "audience": 35 },
+      {"playId": "othello", "audience": 40 }
+    ]
+  }
+}