Spelling, simplification, and effective if improvements (#339)

diff --git a/cel/env.go b/cel/env.go
index b1ae0b2..0919191 100644
--- a/cel/env.go
+++ b/cel/env.go
@@ -105,7 +105,7 @@
 	return NewCustomEnv(stdOpts...)
 }
 
-// NewCustomEnv creates a custom program enviroment which is not automatically configured with the
+// NewCustomEnv creates a custom program environment which is not automatically configured with the
 // standard library of functions and macros documented in the CEL spec.
 //
 // The purpose for using a custom environment might be for subsetting the standard library produced
diff --git a/examples/simple_test.go b/examples/simple_test.go
index c4a6ea7..5d24d83 100644
--- a/examples/simple_test.go
+++ b/examples/simple_test.go
@@ -34,9 +34,15 @@
 		log.Fatalln(iss.Err())
 	}
 	prg, err := env.Program(ast)
+	if err != nil {
+		log.Fatalln(err)
+	}
 	out, _, err := prg.Eval(map[string]interface{}{
 		"name": "CEL",
 	})
+	if err != nil {
+		log.Fatalln(err)
+	}
 	fmt.Println(out)
 	// Output:Hello world! I'm CEL.
 }
diff --git a/interpreter/attribute_patterns_test.go b/interpreter/attribute_patterns_test.go
index d3fde73..57c1713 100644
--- a/interpreter/attribute_patterns_test.go
+++ b/interpreter/attribute_patterns_test.go
@@ -296,7 +296,7 @@
 	// Qualify a[b] with 'c', a[b].c
 	c, _ := fac.NewQualifier(nil, 3, "c")
 	a.AddQualifier(c)
-	// The resolve step should return unkonwn
+	// The resolve step should return unknown
 	val, err = a.Resolve(partVars)
 	if err != nil {
 		t.Fatal(err)
diff --git a/interpreter/interpreter_test.go b/interpreter/interpreter_test.go
index 333926d..3438b60 100644
--- a/interpreter/interpreter_test.go
+++ b/interpreter/interpreter_test.go
@@ -382,7 +382,7 @@
 				"pb2": &proto2pb.TestAllTypes{
 					RepeatedBool: []bool{false},
 					MapInt64NestedType: map[int64]*proto2pb.NestedTestAllTypes{
-						1: &proto2pb.NestedTestAllTypes{},
+						1: {},
 					},
 					MapStringString: map[string]string{},
 				},
@@ -409,7 +409,7 @@
 				"pb3": &proto3pb.TestAllTypes{
 					RepeatedBool: []bool{false},
 					MapInt64NestedType: map[int64]*proto3pb.NestedTestAllTypes{
-						1: &proto3pb.NestedTestAllTypes{},
+						1: {},
 					},
 					MapStringString: map[string]string{},
 				},