add current_role function

Author: imtbkcat

go.mod1

@@ -11,6 +11,7 @@ require (
 	github.com/pingcap/errors v0.11.0
 	github.com/pingcap/tidb v0.0.0-20190218065808-69472bd1a6e9
 	github.com/pingcap/tipb v0.0.0-20190107072121-abbec73437b7
+	github.com/shirou/gopsutil v2.18.12+incompatible // indirect
 	github.com/sirupsen/logrus v1.3.0
 	golang.org/x/text v0.3.1-0.20180807135948-17ff2d5776d2
 )

go.sum1

@@ -94,6 +94,8 @@ github.com/remyoudompheng/bigfft v0.0.0-20170806203942-52369c62f446 h1:/NRJ5vAYo
 github.com/remyoudompheng/bigfft v0.0.0-20170806203942-52369c62f446/go.mod h1:uYEyJGbgTkfkS4+E/PavXkNJcbFIpEtjt2B0KDQ5+9M=
 github.com/shirou/gopsutil v2.18.10+incompatible h1:cy84jW6EVRPa5g9HAHrlbxMSIjBhDSX0OFYyMYminYs=
 github.com/shirou/gopsutil v2.18.10+incompatible/go.mod h1:5b4v6he4MtMOwMlS0TUMTu2PcXUg8+E1lC7eC3UO/RA=
+github.com/shirou/gopsutil v2.18.12+incompatible h1:1eaJvGomDnH74/5cF4CTmTbLHAriGFsTZppLXDX93OM=
+github.com/shirou/gopsutil v2.18.12+incompatible/go.mod h1:5b4v6he4MtMOwMlS0TUMTu2PcXUg8+E1lC7eC3UO/RA=
 github.com/shurcooL/httpfs v0.0.0-20171119174359-809beceb2371/go.mod h1:ZY1cvUeJuFPAdZ/B6v7RHavJWZn2YPVFQ1OSXhCGOkg=
 github.com/shurcooL/vfsgen v0.0.0-20181020040650-a97a25d856ca/go.mod h1:TrYk7fJVaAttu97ZZKrO9UbRa8izdowaMIZcxYMbVaw=
 github.com/sirupsen/logrus v1.2.0/go.mod h1:LxeOpSwHxABJmUn/MG1IvRgCAasNZTLOkJPxbbu5VWo=

misc.go

@@ -204,6 +204,7 @@ var tokenMap = map[string]int{
 	"CURRENT_TIME":             currentTime,
 	"CURRENT_TIMESTAMP":        currentTs,
 	"CURRENT_USER":             currentUser,
+	"CURRENT_ROLE":             currentRole,
 	"CURTIME":                  curTime,
 	"DATA":                     data,
 	"DATABASE":                 database,