[chore] update viper version (#2539)

* update viper version

* removes our last uses of the slice package

* fix tests

vendor/github.com/sourcegraph/conc/waitgroup.go

@@ -0,0 +1,52 @@
+package conc
+
+import (
+	"sync"
+
+	"github.com/sourcegraph/conc/panics"
+)
+
+// NewWaitGroup creates a new WaitGroup.
+func NewWaitGroup() *WaitGroup {
+	return &WaitGroup{}
+}
+
+// WaitGroup is the primary building block for scoped concurrency.
+// Goroutines can be spawned in the WaitGroup with the Go method,
+// and calling Wait() will ensure that each of those goroutines exits
+// before continuing. Any panics in a child goroutine will be caught
+// and propagated to the caller of Wait().
+//
+// The zero value of WaitGroup is usable, just like sync.WaitGroup.
+// Also like sync.WaitGroup, it must not be copied after first use.
+type WaitGroup struct {
+	wg sync.WaitGroup
+	pc panics.Catcher
+}
+
+// Go spawns a new goroutine in the WaitGroup.
+func (h *WaitGroup) Go(f func()) {
+	h.wg.Add(1)
+	go func() {
+		defer h.wg.Done()
+		h.pc.Try(f)
+	}()
+}
+
+// Wait will block until all goroutines spawned with Go exit and will
+// propagate any panics spawned in a child goroutine.
+func (h *WaitGroup) Wait() {
+	h.wg.Wait()
+
+	// Propagate a panic if we caught one from a child goroutine.
+	h.pc.Repanic()
+}
+
+// WaitAndRecover will block until all goroutines spawned with Go exit and
+// will return a *panics.Recovered if one of the child goroutines panics.
+func (h *WaitGroup) WaitAndRecover() *panics.Recovered {
+	h.wg.Wait()
+
+	// Return a recovered panic if we caught one from a child goroutine.
+	return h.pc.Recovered()
+}