2020/03/16 21:50:56 failed to parse matching URL: parse "http://%s:5000/api/agent/v1": invalid URL escape "%s:"
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x20 pc=0x11a5cfb]

goroutine 3917 [running]:
go/types.(*operand).assignableTo(0xc00d0f89a0, 0x0, 0x0, 0x0, 0x0, 0xc00d0f8c28)
/usr/local/go/src/go/types/operand.go:219 +0xfb
go/types.AssignableTo(...)
/usr/local/go/src/go/types/api.go:360
golang.org/x/tools/internal/lsp/source.(*candidateInference).typeMatches(0xc00342b0a0, 0x0, 0x0, 0x1a056a0, 0xc00bac0370, 0xc00d0f89e8)
/Users/fengcheng/go/pkg/mod/golang.org/x/tools@v0.0.0-20200227200655-6862ededa516/internal/lsp/source/completion.go:1972 +0xdf
golang.org/x/tools/internal/lsp/source.(*candidateInference).assigneesMatch(0xc00342b0a0, 0xc00d0f8c28, 0xc0027d23c0, 0x2)
/Users/fengcheng/go/pkg/mod/golang.org/x/tools@v0.0.0-20200227200655-6862ededa516/internal/lsp/source/completion.go:2029 +0x19b
golang.org/x/tools/internal/lsp/source.(*completer).matchingCandidate(0xc00342b000, 0xc00d0f8c28, 0xc00bac00a0)
/Users/fengcheng/go/pkg/mod/golang.org/x/tools@v0.0.0-20200227200655-6862ededa516/internal/lsp/source/completion.go:1872 +0x119
golang.org/x/tools/internal/lsp/source.(*completer).found(0xc00342b000, 0x1a247c0, 0xc00bac04b0, 0x3ff0000000000000, 0x0, 0x0, 0x10000, 0x0, 0x0)
/Users/fengcheng/go/pkg/mod/golang.org/x/tools@v0.0.0-20200227200655-6862ededa516/internal/lsp/source/completion.go:336 +0x128
golang.org/x/tools/internal/lsp/source.(*completer).methodsAndFields(0xc00342b000, 0x1a05720, 0xc00bab1ef0, 0x1, 0x0, 0x7f, 0x1)
/Users/fengcheng/go/pkg/mod/golang.org/x/tools@v0.0.0-20200227200655-6862ededa516/internal/lsp/source/completion.go:811 +0x15a
golang.org/x/tools/internal/lsp/source.(*completer).deepSearch(0xc00342b000, 0x1a24ae0, 0xc006f0c140, 0x3feca69c691cc3f2, 0xc00d2ffd8c, 0x4, 0x10000, 0x0, 0x0)
/Users/fengcheng/go/pkg/mod/golang.org/x/tools@v0.0.0-20200227200655-6862ededa516/internal/lsp/source/deep_completion.go:191 +0x1c6
golang.org/x/tools/internal/lsp/source.(*completer).found(0xc00342b000, 0x1a24ae0, 0xc006f0c140, 0x3feca69c691cc3f2, 0xc00d2ffd8c, 0x4, 0x10000, 0x0, 0x0)
/Users/fengcheng/go/pkg/mod/golang.org/x/tools@v0.0.0-20200227200655-6862ededa516/internal/lsp/source/completion.go:368 +0x29a
golang.org/x/tools/internal/lsp/source.(*completer).lexical(0xc00342b000, 0x0, 0x0)
/Users/fengcheng/go/pkg/mod/golang.org/x/tools@v0.0.0-20200227200655-6862ededa516/internal/lsp/source/completion.go:916 +0x739
golang.org/x/tools/internal/lsp/source.Completion(0x1a12360, 0xc00d0e29f0, 0x1a24540, 0xc006a6a600, 0x1a10a20, 0xc006a6a5a0, 0x4053400000000000, 0x4033000000000000, 0x0, 0x0, ...)
/Users/fengcheng/go/pkg/mod/golang.org/x/tools@v0.0.0-20200227200655-6862ededa516/internal/lsp/source/completion.go:564 +0xe02
golang.org/x/tools/internal/lsp.(*Server).completion(0xc0001e1d80, 0x1a12360, 0xc002b5ac90, 0xc006be0d20, 0x0, 0x0, 0xc006b58160)
/Users/fengcheng/go/pkg/mod/golang.org/x/tools@v0.0.0-20200227200655-6862ededa516/internal/lsp/completion.go:27 +0x6b0
golang.org/x/tools/internal/lsp.(*Server).Completion(0xc0001e1d80, 0x1a12360, 0xc002b5ac90, 0xc006be0d20, 0xc006be0d20, 0x0, 0x0)
/Users/fengcheng/go/pkg/mod/golang.org/x/tools@v0.0.0-20200227200655-6862ededa516/internal/lsp/server_gen.go:24 +0x49
golang.org/x/tools/internal/lsp/protocol.serverHandler.Deliver(0x1a2cb40, 0xc0001e1d80, 0x1a12360, 0xc002b5ac90, 0xc002940040, 0x0, 0x0)
/Users/fengcheng/go/pkg/mod/golang.org/x/tools@v0.0.0-20200227200655-6862ededa516/internal/lsp/protocol/tsserver.go:345 +0x2064
golang.org/x/tools/internal/jsonrpc2.(*Conn).Run.func1(0xc001f12e40, 0xc002940040, 0xc0003656e0, 0x1a12360, 0xc002b5ac90, 0x0, 0x0, 0xc00097d7d0)
/Users/fengcheng/go/pkg/mod/golang.org/x/tools@v0.0.0-20200227200655-6862ededa516/internal/jsonrpc2/jsonrpc2.go:372 +0x160
created by golang.org/x/tools/internal/jsonrpc2.(*Conn).Run
/Users/fengcheng/go/pkg/mod/golang.org/x/tools@v0.0.0-20200227200655-6862ededa516/internal/jsonrpc2/jsonrpc2.go:356 +0x850

Process gopls stderr<2> finished

the code that contains url.

return fmt.Sprintf("http://%s:5000/api/agent/v1", "")