Add Produce The Zero Value Of A Generic Type as a Go TIL

Author: jbranchaud

README.md

@@ -10,7 +10,7 @@ pairing with smart people at Hashrocket.
 
 For a steady stream of TILs, [sign up for my newsletter](https://crafty-builder-6996.ck.page/e169c61186).
 
-_1543 TILs and counting..._
+_1544 TILs and counting..._
 
 ---
 
@@ -412,6 +412,7 @@ _1543 TILs and counting..._
 - [Not So Random](go/not-so-random.md)
 - [Parse A String Into Individual Fields](go/parse-a-string-into-individual-fields.md)
 - [Parse Flags From CLI Arguments](go/parse-flags-from-cli-arguments.md)
+- [Produce The Zero Value Of A Generic Type](go/produce-the-zero-value-of-a-generic-type.md)
 - [Redirect File To Stdin During Delve Debug](go/redirect-file-to-stdin-during-delve-debug.md)
 - [Replace The Current Process With An External Command](go/replace-the-current-process-with-an-external-command.md)
 - [Sleep For A Duration](go/sleep-for-a-duration.md)

go/produce-the-zero-value-of-a-generic-type.md

@@ -0,0 +1,32 @@
+# Produce The Zero Value For A Generic Type
+
+While writing a _pop_ function that would work with slices of a generic type, I
+ran into the issue of needing to produce a zero value of type `T` when
+returning early for an empty slice.
+
+The way to arbitrarily get the zero value of a generic in Go is with `*new(T)`.
+
+I was able to use this in my `Pop` function like so:
+
+```go
+func Pop[T any](slice []T) (T, error) {
+	if len(slice) == 0 {
+		return *new(T), fmt.Errorf("cannot pop an empty slice")
+	}
+
+	lastItem := slice[len(slice)-1]
+
+	slice = slice[:len(slice)-1]
+
+	return lastItem, nil
+}
+```
+
+If this is happening in multiple functions and we want a more self-documenting
+approach, we can pull it out into a function `zero`:
+
+```go
+func zero[T any]() T {
+	return *new(T)
+}
+```