porters-handbook: Fix typos

Reviewed by:	ygy
Differential Revision:	https://reviews.freebsd.org/D29096

documentation/content/en/books/porters-handbook/special/chapter.adoc

@@ -713,7 +713,7 @@ For ports that use Go, define `USES=go`. Refer to <<uses-go,`go`>> for a list of
 .Creating a Port for a Go Modules Based Application
 [example]
 ====
-In most cases, it is sufficient to set `GO_MODULE` variable to the value specified by `module` directive in `go.mod`:
+In most cases, it is sufficient to set the `GO_MODULE` variable to the value specified by the `module` directive in `go.mod`:
 
 [.programlisting]
 ....

documentation/content/en/books/porters-handbook/uses/chapter.adoc

@@ -520,7 +520,7 @@ Sets default values and targets used to build Go software. A build dependency on
 The build process is controlled by several variables:
 
 `GO_MODULE`::
-The name of the application module as specified by `module` directive in `go.mod`. In most cases, this is the only requred variable for ports that use Go modules.
+The name of the application module as specified by the `module` directive in `go.mod`. In most cases, this is the only required variable for ports that use Go modules.
 
 `GO_PKGNAME`::
 The name of the Go package when building in GOPATH mode. This is the directory that will be created in `${GOPATH}/src`. If not set explicitly and `GH_SUBDIR` or `GL_SUBDIR` is present, `GO_PKGNAME` will be inferred from it. It is not needed when building in modules-aware mode.