refactor: replace ioutil=>io; update linter (#1211)

syft/file/classifier.go

@@ -3,7 +3,7 @@ package file
 import (
 	"bytes"
 	"fmt"
-	"io/ioutil"
+	"io"
 	"regexp"
 	"text/template"
 
@@ -84,7 +84,7 @@ func (c Classifier) Classify(resolver source.FileResolver, location source.Locat
 	defer internal.CloseAndLogError(contentReader, location.VirtualPath)
 
 	// TODO: there is room for improvement here, as this may use an excessive amount of memory. Alternate approach is to leverage a RuneReader.
-	contents, err := ioutil.ReadAll(contentReader)
+	contents, err := io.ReadAll(contentReader)
 	if err != nil {
 		return nil, err
 	}

syft/file/secrets_cataloger.go

@@ -4,7 +4,6 @@ import (
 	"bytes"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"regexp"
 	"sort"
 
@@ -111,7 +110,7 @@ func extractValue(resolver source.FileResolver, location source.Location, start,
 	}
 	defer internal.CloseAndLogError(readCloser, location.VirtualPath)
 
-	n, err := io.CopyN(ioutil.Discard, readCloser, start)
+	n, err := io.CopyN(io.Discard, readCloser, start)
 	if err != nil {
 		return "", fmt.Errorf("unable to read contents for location=%q : %w", location, err)
 	}

syft/file/secrets_search_by_line_strategy.go

@@ -5,7 +5,6 @@ import (
 	"errors"
 	"fmt"
 	"io"
-	"io/ioutil"
 	"regexp"
 
 	"github.com/anchore/syft/internal"
@@ -79,7 +78,7 @@ func readerAtPosition(resolver source.FileResolver, location source.Location, se
 		return nil, fmt.Errorf("unable to fetch reader for location=%q : %w", location, err)
 	}
 	if seekPosition > 0 {
-		n, err := io.CopyN(ioutil.Discard, readCloser, seekPosition)
+		n, err := io.CopyN(io.Discard, readCloser, seekPosition)
 		if err != nil {
 			return nil, fmt.Errorf("unable to read contents for location=%q while searching for secrets: %w", location, err)
 		}