diff --git a/.ci/Dockerfile b/.ci/Dockerfile
index 6676568d916..3311f6585a4 100644
--- a/.ci/Dockerfile
+++ b/.ci/Dockerfile
@@ -7,7 +7,8 @@ ENV GO111MODULE=off
 RUN apk add --no-cache --quiet make curl git jq unzip tree && \
      apk add bash && \
      go get golang.org/x/sync/errgroup && \
-     go get golang.org/x/xerrors
+     go get golang.org/x/xerrors && \
+     go get github.com/hashicorp/golang-lru
 
 VOLUME /go/src/golang.org/x/tools
 WORKDIR /go/src/golang.org/x/tools
diff --git a/.travis.yml b/.travis.yml
index 9693d38545f..1ffc78ffd88 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -24,6 +24,7 @@ env:
 before_install:
   - go get golang.org/x/sync/errgroup
   - go get golang.org/x/xerrors
+  - go get github.com/hashicorp/golang-lru
 
 matrix:
   fast_finish: true
diff --git a/appveyor.yml b/appveyor.yml
index a365cf389e9..ee3fa5d0aae 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -26,6 +26,7 @@ environment:
 build_script:
   - go get golang.org/x/sync/errgroup
   - go get golang.org/x/xerrors
+  - go get github.com/hashicorp/golang-lru
   # TODO(henrywong) For now, there are problems about the windows test.
   # - go test ./internal/lsp -v
   - mkdir go-langserver-windows
diff --git a/go.mod b/go.mod
index 026a2638844..28a70df3b20 100644
--- a/go.mod
+++ b/go.mod
@@ -3,6 +3,7 @@ module golang.org/x/tools
 go 1.11
 
 require (
+	github.com/hashicorp/golang-lru v0.5.3
 	golang.org/x/net v0.0.0-20190620200207-3b0461eec859
 	golang.org/x/sync v0.0.0-20190423024810-112230192c58
 	golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7
diff --git a/go.sum b/go.sum
index c4cc4a6d321..6d3e7f7e802 100644
--- a/go.sum
+++ b/go.sum
@@ -1,3 +1,5 @@
+github.com/hashicorp/golang-lru v0.5.3 h1:YPkqC67at8FYaadspW/6uE0COsBxS2656RLEr8Bppgk=
+github.com/hashicorp/golang-lru v0.5.3/go.mod h1:iADmTwqILo4mZ8BN3D2Q6+9jd8WM5uGBxy+E8yxSoD4=
 golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859 h1:R/3boaszxrf1GEUWTVDzSKVwLmSJpwZ1yqXm8j0v2QI=
 golang.org/x/net v0.0.0-20190620200207-3b0461eec859/go.mod h1:z5CRVTTTmAJ677TzLLGU+0bjPO0LkuOLi4/5GtJWs/s=
diff --git a/go/packages/golist.go b/go/packages/golist.go
index 9f8d4ced77c..8c3594e3796 100644
--- a/go/packages/golist.go
+++ b/go/packages/golist.go
@@ -9,6 +9,7 @@ import (
 	"encoding/json"
 	"fmt"
 	"go/types"
+	"hash/fnv"
 	"io/ioutil"
 	"log"
 	"os"
@@ -22,6 +23,7 @@ import (
 	"sync"
 	"time"
 
+	"github.com/hashicorp/golang-lru"
 	"golang.org/x/tools/go/internal/packagesdriver"
 	"golang.org/x/tools/internal/gopathwalk"
 	"golang.org/x/tools/internal/semver"
@@ -91,7 +93,7 @@ func goListDriver(cfg *Config, patterns ...string) (*driverResponse, error) {
 	var rootDirs map[string]string
 	var rootDirsReady = make(chan struct{})
 	go func() {
-		rootDirs = determineRootDirs(cfg)
+		rootDirs = determineRootDirsLRUCached(cfg)
 		close(rootDirsReady)
 	}()
 	getRootDirs := func() map[string]string {
@@ -101,7 +103,7 @@ func goListDriver(cfg *Config, patterns ...string) (*driverResponse, error) {
 
 	// always pass getRootDirs to golistDriver
 	golistDriver := func(cfg *Config, patterns ...string) (*driverResponse, error) {
-		return golistDriver(cfg, getRootDirs, patterns...)
+		return golistDriverLRUCached(cfg, getRootDirs, patterns...)
 	}
 
 	// Determine files requested in contains patterns
@@ -597,6 +599,36 @@ func otherFiles(p *jsonPackage) [][]string {
 	return [][]string{p.CFiles, p.CXXFiles, p.MFiles, p.HFiles, p.FFiles, p.SFiles, p.SwigFiles, p.SwigCXXFiles, p.SysoFiles}
 }
 
+type goListResult struct {
+	response *driverResponse
+	err      error
+}
+
+var (
+	goListLRUCache       *lru.Cache
+	createGoListLRUCache sync.Once
+	goListLRUEntries     = 16 * 32
+)
+
+func golistDriverLRUCached(cfg *Config, rootsDirs func() map[string]string, words ...string) (*driverResponse, error) {
+	createGoListLRUCache.Do(func() {
+		goListLRUCache, _ = lru.New(goListLRUEntries)
+	})
+
+	h := fnv.New32a()
+	h.Write([]byte(cfg.Dir))
+	h.Write([]byte(words[len(words)-1]))
+	hashKey := h.Sum32()
+	if val, ok := goListLRUCache.Get(hashKey); ok {
+		res := val.(goListResult)
+		return res.response, res.err
+	} else {
+		res, err := golistDriver(cfg, rootsDirs, words...)
+		goListLRUCache.Add(hashKey, goListResult{res, err})
+		return res, err
+	}
+}
+
 // golistDriver uses the "go list" command to expand the pattern
 // words and return metadata for the specified packages. dir may be
 // "" and env may be nil, as per os/exec.Command.
diff --git a/go/packages/golist_overlay.go b/go/packages/golist_overlay.go
index b051327df66..45075d36492 100644
--- a/go/packages/golist_overlay.go
+++ b/go/packages/golist_overlay.go
@@ -10,6 +10,9 @@ import (
 	"path/filepath"
 	"strconv"
 	"strings"
+	"sync"
+
+	"github.com/hashicorp/golang-lru"
 )
 
 // processGolistOverlay provides rudimentary support for adding
@@ -194,6 +197,30 @@ func hasTestFiles(p *Package) bool {
 	return false
 }
 
+type determineRootDirsResult struct {
+	roots map[string]string
+}
+
+var (
+	determineRootDirsLRUCache *lru.Cache
+	createRootLRUCache        sync.Once
+	rootLRUEntries            = 16
+)
+
+func determineRootDirsLRUCached(cfg *Config) map[string]string {
+	createRootLRUCache.Do(func() {
+		determineRootDirsLRUCache, _ = lru.New(rootLRUEntries)
+	})
+	if val, ok := determineRootDirsLRUCache.Get(cfg.Dir); ok {
+		res := val.(determineRootDirsResult)
+		return res.roots
+	} else {
+		roots := determineRootDirs(cfg)
+		determineRootDirsLRUCache.Add(cfg.Dir, determineRootDirsResult{roots})
+		return roots
+	}
+}
+
 // determineRootDirs returns a mapping from directories code can be contained in to the
 // corresponding import path prefixes of those directories.
 // Its result is used to try to determine the import path for a package containing