feat(sql): add database/sql plugin

[kagaya85]

Add go2sky plugin for database/sql

This PR is still WIP and may need sufficient tests before merge

Because this is a new plugin, we may need to discuss some implementation details

Any comments or suggestions are welcome, thanks in advance

[rainbend]

Hi @kagaya85 please update the license header :)

[kagaya85]

Now, the Tx struct contains a context of the transaction local span

if user use methods with context that contains span context, like ExecContext, new exit span will follow the span in the context, in addition, for methods without context(Exec, Query) or context do not contain span, new exit span will follow the local span in Tx struct

type Tx struct {
	*sql.Tx

	db   *DB
	span go2sky.Span
	ctx  context.Context
}

func (tx *Tx) Exec(query string, args ...interface{}) (sql.Result, error) {
	return tx.ExecContext(tx.ctx, query, args)
}

func (tx *Tx) ExecContext(ctx context.Context, query string, args ...interface{}) (sql.Result, error) {
	if id := go2sky.SpanID(ctx); id == go2sky.EmptySpanID {
		// if ctx do not contain parent span, use transaction ctx instead
		ctx = tx.ctx
	}
	span, err := createSpan(ctx, tx.db.tracer, tx.db.opts, "execute")
	if err != nil {
		return nil, err
	}
	defer span.End()

	...

	return res, err
}

[kagaya85]

@arugal For the previous implementation, is it possible to keep it as a new plugin which based on database/sql/driver?
this can lead to more detailed tracking and flexibility, such as using in some third-party sql libaray like sqlx

[rainbend]

@arugal For the previous implementation, is it possible to keep it as a new plugin which based on database/sql/driver?
this can lead to more detailed tracking and flexibility, such as using in some third-party sql libaray like sqlx

Good idea, we can do this in a new PR, after the current PR is merged.

[rainbend]

LGTM

Local Test Results

Database

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