Move basic example into its own subdirectory (#25)

This makes it more obvious (without having to look at the code) that
the basic example is actually an example, rather than something tied to
the other examples or some sort of metadata file.

example/basic/main.go

@@ -0,0 +1,92 @@
+// Copyright 2019, OpenTelemetry Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package main
+
+import (
+	"context"
+
+	"github.com/open-telemetry/opentelemetry-go/api/metric"
+	"github.com/open-telemetry/opentelemetry-go/api/stats"
+	"github.com/open-telemetry/opentelemetry-go/api/tag"
+	"github.com/open-telemetry/opentelemetry-go/api/trace"
+
+	"github.com/open-telemetry/opentelemetry-go/api/event"
+	"github.com/open-telemetry/opentelemetry-go/exporter/loader"
+)
+
+var (
+	tracer = trace.GlobalTracer().
+		WithComponent("example").
+		WithResources(
+			tag.New("whatevs").String("yesss"),
+		)
+
+	fooKey     = tag.New("ex.com/foo", tag.WithDescription("A Foo var"))
+	barKey     = tag.New("ex.com/bar", tag.WithDescription("A Bar var"))
+	lemonsKey  = tag.New("ex.com/lemons", tag.WithDescription("A Lemons var"))
+	anotherKey = tag.New("ex.com/another")
+
+	oneMetric = metric.NewFloat64Gauge("ex.com/one",
+		metric.WithKeys(fooKey, barKey, lemonsKey),
+		metric.WithDescription("A gauge set to 1.0"),
+	)
+
+	measureTwo = tag.NewMeasure("ex.com/two")
+)
+
+func main() {
+	ctx := context.Background()
+
+	ctx = tag.NewContext(ctx,
+		tag.Insert(fooKey.String("foo1")),
+		tag.Insert(barKey.String("bar1")),
+	)
+
+	gauge := oneMetric.Gauge(
+		fooKey.Value(ctx),
+		barKey.Value(ctx),
+		lemonsKey.Int(10),
+	)
+
+	err := tracer.WithSpan(ctx, "operation", func(ctx context.Context) error {
+
+		trace.SetError(ctx, true)
+
+		trace.Active(ctx).AddEvent(ctx, event.WithAttr("Nice operation!", tag.New("bogons").Int(100)))
+
+		trace.Active(ctx).SetAttributes(anotherKey.String("yes"))
+
+		gauge.Set(ctx, 1)
+
+		return tracer.WithSpan(
+			ctx,
+			"Sub operation...",
+			func(ctx context.Context) error {
+				trace.Active(ctx).SetAttribute(lemonsKey.String("five"))
+
+				trace.Active(ctx).AddEvent(ctx, event.WithString("Format schmormat %d!", 100))
+
+				stats.Record(ctx, measureTwo.M(1.3))
+
+				return nil
+			},
+		)
+	})
+	if err != nil {
+		panic(err)
+	}
+
+	loader.Flush()
+}